What are the major sects of Buddhism?
Mahayana is not a sect at all; it is a vehicle.

Major traditions in Buddhism are usually country or region related. We can distinguish three major branches of Buddhism in the World by what they keep as canon.


Tibetan, Mongolian, and Russian Buddhism share Tibetan canon.
Chinese, Japanese, and Korean Buddhism share Chinese canon.
Sri Lanka, Burma, Thailand, etc share Pali canon.


Some countries mix several aforementioned branches.