What dose 'str' mean?

Answer 1

You mean str()? It's a method that converts other types to string.
https://www.programiz.com/JUMP_LINK__&&__python__&&__JUMP_LINK-programming/methods/built-in/str

Answer 2

str() or ‘’ or “”

Answer 3

String (text like "This is a string". Text like This is a string is not a string.)