What is likely the main purpose of providing stage directions in a drama?

a myth is something that is told for many years that u go looking for and cant find and a truth is something that u can find in real life and can be story's of for example:

mermaid's and unicorns: u can't find them at all so they can be a myth cause u hear story's about them once u go looking for them u won't find them.

dinassours(can't spell): u hear story's about them at school by ur friends and one day ur dad takes u to a museum and u find fossils of them so u realize they are real and not fake.