Categories of religion
Question

What are the different categories of religion that exist in the world?
Praise be to Allah.People are divided according to their religions into two categories: 
1 – Those who have a Book that was revealed from Allah, such as the Jews, Christians and Muslims. The Jews and Christians, because of their lack of knowledge of what was narrated in their books, and because they took humans as lords instead of Allah, and because a long time has passed (since those Books were revealed), have lost their books which Allah revealed to their Prophets. So the rabbis and priests wrote books for them which they claimed came from Allah, but they are not from Allah, rather they are the work of forgers and the distortion of fanatics. 
With regard to the Book of the Muslims (the Holy Quran), it is the last of the Divine Books to be revealed, and the most reliable, and Allah has guaranteed to preserve it – He did not leave that to human beings. Allah says (interpretation of the meaning): 
“Verily, We, it is We Who have sent down the Dhikr (i.e. the Quran) and surely, We will guard it (from corruption)”
[al-Hijr 15:9]
It is preserved in men’s hearts and on paper, because it is the final Book in which is Allah’s guidance for mankind, and He has established it as proof against them until the Hour begins. He has decreed that it will abide and He has created for it in every age people who will follow its guidance, learn it by heart, implement its laws and believe in it.  
2 – Those who do not have a Book that was revealed from Allah, although they may have an inherited book that is attributed to the founder of their religion, such as the Hindus, Magians (Zoroastrians), Buddhists, Confucians and the Arabs before the coming of Muhammad (peace and blessings of Allah be upon him). 
There is no nation that does not have knowledge or act according to what is in their best worldly interests. This is part of the general guidance that Allah has given to all people, and indeed to all animals, as He guides animals to eat food and drink that are good for them, and to avoid those that are harmful. Allah has created in them love for the former and hatred towards the latter. Allah says (interpretation of the meaning): 
“Glorify the Name of your Lord, the Most High,
Who has created (everything), and then proportioned it.
And Who has measured (preordainments for everything even to be blessed or wretched); and then guided (i.e. showed mankind the right as well as the wrong paths, and guided the animals to pasture).”
[al-‘Alaa 87:1-3]
And Moosa (peace be upon him) said to Pharaoh: 
“Our Lord is He Who gave to each thing its form and nature, then guided it aright”
[Ta-Ha 20:50 – interpretation of the meaning]
And Ibraaheem (peace be upon him) said:  
“Who has created me, and it is He Who guides me”
[al-Shu’ara’ 26:87 – interpretation of the meaning]
See al-Jawaab al-Saheeh fiman badala Deen al-Maseeh, vol. 4, p. 97. 
Every intelligent person – who has the slightest insight – knows that the followers of different religions have more beneficial knowledge and do more righteous deeds than those who are not followers of any religion, so there is nothing good to be found with the non-Muslim followers of other religions, and what the Muslims have is more perfect. The followers of different religions have something that others do not have. Knowledge and actions are of two types: 
The first type is knowledge that is acquired through mental reasoning, such as mathematics, medicine and manufacturing. These things are the same for followers of religion and for others, indeed they are more well versed in them. But with regard to matters which cannot be known merely through mental reasoning, such as divine knowledge and knowledge of religions, this is something that belongs only to the followers of religion. This includes matters for which rational evidence can be produced, and the Messengers guided mankind and pointed out to them the rational basis of this knowledge, thus it is rational and shar’i at the same time. 
The second type is that which can only be known from the words of the Messengers. There is no way to acquire this knowledge through mental reasoning. This includes information about Allah, His names and attributes, the reward in the Hereafter for those who obey Him, the punishment for those who disobey Him, His laws, and news of the earlier Prophets and their dealings with their nations. See Majmoo’ Fatawa Shaykh al-Islam Ibn Taymiyah, vol. 4, p. 210-211.