Comparative religion looks at different religions of the world and how they relate to each other. It examines similarities, differences, and the way in which different religions interact and complement each other. Comparative religion is a growing field, and plays an important role in modern discourse as various religious groups find themselves coming into closer contact with one another, on both the personal and social level.

Comparative religion simplifies its task by separating religions down into various supergroups, each of which reflects an overarching tradition and encompasses a number of individual religions. The three major supergroups looked at, which comprise the majority of practitioners on the planet, are the Abrahamic religions, the Taoic religions, and the Indian religions. Other supergroups include the Indigenous religions, the African diasporic religions, the new religions, and the Iranic religions. Even within these supergroups there can be seen a great deal of overlap, and a major area of study within comparative religion is the extent and form of this overlap.

The Abrahamic religions account for more than half of the world population, with nearly four billion adherents, and so often a great deal of focus is given to them within comparative religion studies. The Abrahamic religions are those which have descended from the teachings of Abraham, and include Judaism, Christianity, and Islam. Some modern faiths and movements, such as Baha’i, Rastafarianism, and the Samaritans, are also classified as Abrahamic religions by a number of comparative religion scholars. Movements within these larger classes, such as Mormonism within Christianity, or Sufism within Islam, are also considered part of the larger class. The Abrahamic religions may sometimes be referred to as Western religions in comparative religion, to contrast them with the Eastern religions of the Taoic and Indian groups.

Taoic religions are considered within the field of comparative religion to be those religions which draw their original inspiration from the concept of the Tao, a balancing force that drives the universe. Taoic religions include Taoism itself, Confucianism, and Shinto. Buddhism, an Indian religion, has taken on many Taoic characteristics in East Asia as well, and many Chinese Folk religions have melded Taoic beliefs with traditional indigenous beliefs.

The Indian religions can be seen within a comparative religion analysis as having derived from the Vedic period in India’s past. These religions include Buddhism, Hinduism, Jainism, and Sikhism. Although the Vedas played an important role in the formation of Indian religions, a number of them, including Buddhism, rejected the literal authority of the Vedas, and instead focused on teachings transmitted by figures of the era.

By classifying religions based on their foundational principles and history, comparative religion allows for individual religions to be more easily compared and contrasted. Much of the discussion of comparative religion focuses on intersections between supergroups, such as the merging of indigenous religions with Abrahamic traditions to create entirely novel practices, or the gradual drifting of Chan and Zen Buddhism from its Indian roots towards forms more associated with Taoic religions. Comparative religion also looks at the development of esoteric faiths and mystic traditions within a religion, such as Sufism within Islam, Gnosticism within Christianity, Kabbala within Judaism, Chakra within Hinduism, or Tantra within Buddhism.