HelpMinecraft § text glitch?

Hello, I was always wondering how some people could make their text randomly change characters. I'm pretty sure it has something to do with the "§" key, but I'm not exactly sure. If you know how people do it, please tell me!

^trol post

u need a server that doesn't block that feature and a modded client cuz u can't use § in the normal client
(i think nodus supports this name "hack")