How does the "Rewriterule" command work?

Question

I’m studying about the file .htaccess and how page forwarding occurs. Reading about URL friendly I had doubts about the command RewriteRule, more specifically to its operation, they come just below.

Doubts

1. How the command works RewriteRule and what is its purpose?
2. What types of rules apply to the command RewriteRule?

^{If you can give practical examples, it will facilitate my understanding.}