what is the purpose of fair use laws

Answer 1

The purpose it to balance the greed of thieves against socially useful purposes such as education, debate, and public policy.

Answer 2

Mainly, they indicate what can be freely used by anybody, as opposed to what is copyrighted and either cannot legally be used or can be used with written permission of the owner. ~~> Stories, artwork, photos, lyrics, music ... you name it! Anything humans can create, whether it can be seen/touched or not.

Read lots.
https://www.google.com/search?q=fair+use+laws&oq=fair+use+laws&aqs=chrome..69i57j69i60.2824j0j7&sourceid=chrome&ie=UTF-8