How to connect PHP to Apache?

Question

PHP

Hello!
This is probably a funny question, but I just can't figure out how to choose the FastCGI / CGI connection method and module. Where is this choice? I understand that you need to install php first and then how?
My assumption is that in LoadModule you just change the file. Can you please tell me how to switch between PHP connection method selections to Apache?
PS And yet, the question torments for a long time:
LoadModule php5_module modules/libphp5.so
what kind of file is this? Is it like an Apache module or am I dumb?
Thank you!