What is Credit Union?

Legal Definition
A credit union is a member-owned financial cooperative, democratically controlled by its members, and operated for the purpose of promoting thrift, providing credit at competitive rates, and providing other financial services to its members.

Worldwide, credit union systems vary significantly in terms of total system assets and average institution asset size, ranging from volunteer operations with a handful of members to institutions with assets worth several billion US dollars and hundreds of thousands of members. Credit unions operate alongside other mutuals and cooperatives engaging in cooperative banking, such as building societies.

"Natural-person credit unions" (also called "retail credit unions" or "consumer credit unions") serve individual people, as distinguished from "corporate credit unions," which serve other credit unions.
-- Wikipedia
Legal Definition
a non-profit financial corporation that is organised for the purpose of obtaining credit for its members.