what is #pragma

So I have been trying to figure out what #pragma does. It looks like it calls some libraries but I am not sure. If it is calling libraries, what are available libraries for use and what do these libraries do?

#pragma strict
#pragma implicit
#pragma downcast

Thanks in advance everyone!

pragma is a pre-compiler directive. ie it tells the compiler what to do or how to behave.

eg #strict - “be uptight when you compile this schizzle bro!”