i was wondering how do some people rhite in the backraund
P.S. Please explain whit details i am an idiot

What do you mean by that?
If you mean emotes, type /em your message here (you need to be fighting)
If you mean center texts, type /cp your message here (you need to be op)

Else, I don't see.

Note : you need to be in Multiplayer to use these commands.