belt

A belt is something that you wear around your waist.

A man wears a belt around his waist in order to keep his pants up.
Men and women wear belts that are fashionable.
A belt goes through belt loops on a pair of pants. The belt is fastened with a buckle.

belt and buckle

There are other types of belts:

A seatbelt is worn by a driver and passengers in a car. (To buckle up is to put on a seatbelt.)
A tool belt is worn by a person who does construction work.
A person who is very good at karate earns a black belt.
A conveyor belt moves things from one place to another.