Activate program

Hello!

1. How to activate a running process/program in background and unactivate it if its possible... (so if I start to type, it writes to the program which isn't at the foreground/front)

2. How to activate a running process/program in foreground and unactivate it

with 'unactivate' I meant minimize, hide, make the | of the text...

sry for the low description :<

Cheers!