1. Belief in Allah .

2. Belief in the Prophets.

3. Belief in the Angels.

4. Belief in the Scriptures. (BOOKS OF ALLAH)

5. Belief in the day of judgement.

1.Belief in Allah means:

Belief in One-ness (Tauheed of Allah), His Attributes that is the other names of Allah, His creation, and His Supreme Authority over the whole universe. Tauheed The doctrine of Unity or One-ness of God is the pivot round which the whole system of Islam revolves. It commands the position of the sun in the solar system. A Muslim believes firmly in the fact that Allah is one and only one and he expresses this belief in words and actions. In case a person does not firmly believe in Tauheed, he has a basic defect in his faith of Islam, which amounts to his belonging to the ranks of non-Muslims. All the religions of the world have always affirmed that Allah is One. All the wise men and great scholars of the world have had belief in the One-ness of Allah. The Book of Allah, the Holy Quran, has made the creed of the One-ness of Allah indispensable for Muslims. The earlier Scriptures also preached the Unity of Allah, but due to interpolations made in the text of the Scriptures, and inclusion of facts against the principles of Tauheed the Divine teachings were changed. So, Allah sent His last Prophet Hazrat Muhammad (Peace Be Upon Him) to set the people on the right path and to bring about reformation in their creed. The Holy Quran preaches the doctrine of Tauheed in very elegant form. Some of verses of the Holy Book Quran preaching the creed of the One-ness of Allah are:"Your God is one God; There is no God but he, the Beneficent, the Merciful."(Al-Baqarah:163) "God bears witness, and also the angels and the men of knowledge, That there is no god but He, who upholds justice; there is no god but He, the Mighty, the Wise." (Al-Imran:18) Surah Ikhlas (The Unity is an embodiment of the doctrine of One-ness of Allah and His attributes that He is Alone; none has given Him birth; nor He has given birth to anyone: Say: He is Allah, The One and Only. Allah, The Eternal , Absolute. He begetter not, Nor is He begotten. And there is none like unto Him. (Al-Ikhlas:1-4) There are many implications of the One-ness of Allah, some of which are as follows: Allah is Creator of all things and He is Guardian over all things. (Az-Zumar:62) In another verse Allah says: "Say, Allah is Creator of all things and He is One, the Almighty." (Ar-Ra'd:16) At another place Allah says: "Nothing is as His likeness and He is the Hearer, the Seer." (Ash-Shura:11)
"And Allah is the Sublime Similitude. He is the Mighty, the wise." (An-Nahl:60).
He is the Controller of all the powers attributed to Him. Allah is the only Being who is to be worshipped by man. Man has to seek His pleasure at every step; he begs Allah for his needs and comforts. Allah alone helps man in adversity; He fosters hopes and fears and may do good to or harm His creatures according to His Will. Thus Allah and Allah alone is to be adored and worshipped to become a true Muslim.
THE EXISTENCE OF ALLAH, THE CREATOR:
Just as man has made many wonderful things, and has made enormous progress in science and technology by making such things as electronic-controlled machines and weapons, Allah has made and create the vast Universe of which our earth is only a part. Allah makes they the sun, the earth, the moon, the innumerable stars, the air, the water, the plants and trees and all animals. It is the power of Allah that when He intends to create thing He says, "Kun"! it is done! Allah says in the Holy Quran: "But His Command, when He plan a thing, is only that He Saith unto it, Be and it is." (Ya-Sin:82)
"God is He, who created the heavens and the earth, and sent down from the heaven water, wherewith He brought forth fruits for your provision; and He subjected to you the ships that run on the sea at His command, and He subjected to you the rivers. And He subjected to you the sun and the moon, (going) constant on their courses; and He subjected to you the night and the day." (Ibrahim:32-33)
"It behest not the sun to overtake the moon, nor does the night outstrip the day; and all are floating in an orbit." (Ya-Sin:40)
"Everything We have created in measure." (Al-Qamar: 49) "In the creation of the heavens and earth, and in the alternation of night and day, there are Signs for men of understanding." (Al-Imran: 190)
"So set thy face to the Religion, all-devoted, God's original law on which he originated mankind; there can be no change in God's creation; that is the standing Religion but most men do not know" (Ar-Rum: 30)
SHIRK OR POLLYTHEISM:
The Arabic word Shirk means "to share". In religious sense it means attributing partners with Allah, that is, if a person considers someone else as a share in the Being of Allah and His Attributes, or in the implications of His Attributes, he is an infidel (mushrik,) or Kafir. Shirk is the only sin which is unforgivable. The advice given by Luqman to his son is recorded in the Holy Quran thus: "And when Lokman said to his son admonishing him, `O my son, do not assign associates to God; surely assigning of associates is a mighty wrong'."(Luqman: 13)
The Holy Quran says: "God is He who created you, then provided for you, then He shall make you dead, then He shall give you life; is there any among your associate-gods who does anything of that? Holy be He, Exalted, above that they associate." (Ar-Rum: 40)

2.Belief in the Prophets.

Prophets sent by Allah to mankind to convey His religious injunctions. He has been pleased to send more than one hundred thousand prophets to this world of ours. The first among them was Hazrat Adam(A), while, the last one is our Holy Prophet Hazrat Muhammad (peace be upon him). These prophets came to the world to guide human beings to the straight path of life. They are free from blemishes and sins. Allah, says in the Holy Quran.
"And for every folk there is (sent) a guide".(Ar-Ra'd:7) According to the Holy Quran Prophets were raised from the nations to whom they were sent as Messengers of Allah. They preached in the respective languages of their nations. The Quran says:
"And We never sent a messenger save with the language of his folk that he might make (message) clear for them". (Ibrahim: 4).
Our Holy Prophet Muhammad (peace be upon him) is the last of the line of Prophets. No new Prophet shall ever come after him, and he is the Prophet (Rasool) of all those who would be born till the Day of Judgement. Holy Prophet's Message is for the whole Mankind. Allah had bestowed upon him the honor of being the Leader of all the Prophets and of all men. He did his duty with honesty of purpose and every action of his simplicity and purity characterized. He was simple in habits, simple in food, and simple in dress and in living.
The finality of prophet hood means that after our Holy Prophet Hazrat Muhammad (peace be upon him) no other Prophet will be sent by Allah to this world. The long line of prophet hood, beginning with Hazrat Adam, has come to an end with the Holy Prophet (peace be upon him). Allah says in the Holy Quran:
"Muhammad is not the father of any man among you, but he is the messenger of Allah and the seal of the Prophets." (Al-Ahzab: 40) Seal means 'a device used as a means of keeping closed a letter, a door etc.' Thus the Holy Prophet (peace be upon him) closes the chapter of Prophets, and no other Prophet will come after him till the Day of Judgement.
In the book of traditions by Imam Bokhari, it is stated that Holy Prophet (peace be upon him) once said: " The Prophets used to guide the sons of Israil; when a Prophet died, another Prophet took his place; but there will be no Prophet after me. All the commentators of Islam and the comrades of the Holy Prophet (peace be upon him) agree that the prophet hood has ended with the Holy Prophet (peace be upon him) till the final day and any person claiming prophet hood after him is a liar and an imposter.

3.Belief in the Angels:

Malaikah is plural of malak, meaning an angel. Angels are also creation of Allah like human beings. They are made of light(i.e Noor). They are invisible to us and are neither male nor female. They are always doing the task assigned to them by Allah besides hymning His praise. The number of angels but , there are four of them, who are superior in rank to others.
1. Hazrat Mikail (A)
2. Hazrat Isfrail(A)
3. Hazrat Jibrail(A)
4. Hazrat Izrail (A)
Allah says in the Holy Quran:
"It is no virtue that you turn your faces towards the East and the West, but the virtue is that any believes in God, the Last Day, the angels, the Book and the Prophets, and he gives his wealth, for the love of Him, to orphans, the needy, the traveler, the beggars, and for (ransoming) the enslaved; and he establishes the Prayer and pays the Charity; and they fulfil their promise when they make it and they are patient in hardship and in time of peril; those are the ones who have spoken the truth, and those are the God fearing." (Al_Baqarah: 177)

4.Belief in the Scriptures:

It is already mentioned that it is must for all Muslims to believe on all messengers. Believing on messengers' means that agreed on that they are true Prophets of Allah and their teachings are true. Books revealed on these Prophets are the based on Allah's teachings. So for having believe on Prophets it is must that we also have believe on the books reveals on them. Allah says about the Muslims: "Who believe in what has been sent down to thee and what has been sent down before thee, and they are sure about the Hereafter." (Al-Baqarah: 4)
There are many books but four are most familiar.
1: Zuboor It was revealed to Hazrat Dawood(A)(David).
2: Taurait It was revealed to Hazrat Musa(A)(Moses).
3: Injil It was revealed to Hazrat Isa (A)(Jesus).
4: The Holy Quran, revealed to our Last Holy Prophet Hazrat Muhammad(PBUH).
The Holy Quran is superior to all the Holy Books in many respects, as for instance.
1.Each and every word of Holy Quran is preserved in its original form. Not even a dot has been removed or cancelled. Nor will there be any change in it till the Final Day.
2. The language of the Holy Quran is a miracle
3. The Holy Quran has brought the final Holy Book.
4. The previous scriptures were revealed, all at once, but the revelation of the Holy Quran continued for twenty-three years, bit by bit, as and when necessity arose. Thus it found access to the hearts of the people, and hundreds and thousands of people accepted its codes and commands, and embraced Islam.
5. The Holy Quran is preserved in the hearts of thousands of Muslims. This preservation has continued right from the times of the Holy Prophet (peace be upon him) and Insha-Allah it will continue till the final day. Thus the enemies of Islam have always failed to make any alternation in the Holy text.

5.Belief in the day of judgement:

Belief in the Day of Judgement is one of the most important Lessons of faith of a Muslim. Its importance is mention at numerous places and occasions in the Holy Quran.
"The Calamity! What is the Calamity? What will convey unto thee what the calamity is! A Day wherein mankind will be as thickly scattered moths: and the mountains will become as carded wool." (Al-Qari'ah:1-5).
On the Day of Judgement Hazrat Israfil shall blow the trumpet. Its sound shall be so dreadful and horrible that no one shall survive the shock, all things shall break into pieces, and perish.
The Day of Judgement is sure to come, but Allah only knows when the Day shall come.
Although the time of the day of Judgement is not known to anybody except Allah, our Holy Prophet (Peace Be Upon Him) has indicated a number of signs that indicate that the last day is approaching.
Some of these signs are
1. Disobedience to parents and harsh treatment to them.
2. Singing, dancing and revelries will be in abundance.
3. Younger generation will begin abusing their ancestors.
4. The uneducated and the rustics shall capture position of
5. Low person in society will become an owner of lofty buildings.
6. Incompetent persons will become administrator and rulers.