This is a summary of the World's great religions (with the word great being used to imply numbers of adherents and historical influence rather than any descriptive ideas).
All religions have the function of explaining the world in terms of absolute truths revealed to people at some point in the past. Most religions postulate the existence of one or more intelligent entities responsible for the existence of everything. Most religions deny the existence of death. There is usually an implication that part of the conscience of every human being is eternal. This manifests itself in beliefs of reincarnations and eternal life at the end of the world.
There are many ways of classifying the religions of the world.
One classification is to describe a religion as being either linear or cyclic.
Linear religions have a beginning an end, one life, and (usually) some kind of judgment day at the end. Christianity, Islam, Judaism, and Parsees are linear. Cyclic religions have the idea of birth, death and rebirth, with reincarnation a major theme. Hinduism, Buddhism, Jainism are cyclic.
Another classification is by deity numbers. Monotheistic religions (from the Greek single god) have one god. Often however, there are polytheistic elements (like the Trinity, saints, angels, devils, etc). The monotheistic religions are Judaism, Christianity, Islam, Parsees, Sikhism and the Bahai.
Polytheistic religions have many gods. Most primitive or animistic religions are essentially polytheistic. Hinduism is the one major religion with many gods.
Finally, there are Atheistic religions (Greek: without god). These have no creator god as such (although there may be spirits and other exotic entities). Buddhism is an example (the Buddha is a human who has reached enlightenment), Jainism (with its Tirthankas, or teachers), Confucianism, Taoism (these last two are more philosophies than god-driven religions).
In a historical sense, religions do not just spring up from nothing. There is an evolutionary progression of ideas leading from one religion to another. Sometimes a number of religions compete for pre-eminence at a historical period only for some accident to favor one over the others. The major religions of the world are discussed below in two groups: the linear, monotheistic religions of the West, followed by the polytheistic and atheistic religions of the East. Within these loose groupings, the discussions are vaguely chronological.