The three Abrahamic religions are Judaism, Christianity, and Islam. They are similar in that they claim the patriarch Abraham as a central figure in their family and spiritual genealogies. As a starting point for comparison, we have first of all a shared geographic origin and then on closer investigation, these three religions have a shared origin based on genealogy. However, if you look in more detail at origin, you find that Judaism and Islam diverge.
This idea of origin is emphasized for several reasons. In comparative religion, you might want to know where religion begins in people's lives, how it functions in their lives, and how it is maintained or forgotten. Origin is emphasized at this point as well because the Western Abrahamic religions share the belief that there is only one god. They are grouped together and referred to as the monotheistic traditions.
If you look at the second category of religions, the Indian religions, you notice that they don't adhere to a single supernatural deity. Because of this commonality among the Indian religions they are considered non-theistic, not relating to a single god in the way that the Western religions do. Two Indian religions that share a common geographic origin are Hinduism and Buddhism. while there are a lot of overlapping of ideology, belief, and practice, there are also many differences.
One point of commonality is that they share linguistic origin. Most of the Hindu and Buddhist sacred texts were written in Sanskrit and Pali, closely related in the family of Indo-European languages. They do diverge, however, in terms of geography such as where they migrated to and flourished at certain points in history. If you study this movement in more detail, you would find many interesting points of difference in terms of practice, ritual, custom, and belief.
The third category of religions is the Taoic religions. These are the religions of East Asia and include Taoism, Shintoism, and Confucianism.
What these religions share is a belief in the eternal flow and balance of the universe: the Tao. Living in sync with this universal harmonizing energy is the goal. Followers these religions seek to see and live in the reflection of this ordering, balancing force.
Again, as with the other two main groups of religion, there are particular differences as well. In the Taoic religions, these variations can mostly be observed in terms of emphasis and priority given to certain principles and practices.
After tracing all that historically, sociologically, anthropologically, et cetera, you might just find yourself back with the question, where does religion begin in a life, in a culture, in a people?
The question of origin which seems to pose such a problem from within the religions themselves in many cases is something to keep in mind when studying and comparing religions.
Source: This work is adapted from Sophia author Ted Fairchild.
Any of the religions that claim Abraham as an ancestor, namely Judaism, Christianity, and Islam.
Any religion originating on the Indian subcontinent.
Any religion originating in east Asia.
A discipline that takes as its subject the scholarly examination and comparison of the beliefs, rituals, customs, and traditions of all active religions.