Well well, roleplay (for me) is writing a story with other persons. Each persons take cares of one character and write the story in their perspective and react to the other characters. There is mostly AU roleplays and Non-AU (AU + alternatine univers) AU is playing a character example Taemin (Shinee) but with the personality you want them to have. He is no longer an Idol but a simple student. He can be older or younger than his real age. Actually, you simply use Taemin as a reference of how your character looks like nothing else.

Non-AU is you are playing as Taeming from Shinee. You are and idol you are a shinee member and you interact with other shinee members or other idols and act out the way you thing he is in real life. Personally, I do not like this type since people tend to be overly cliche and other (those are the real bad case) can not like the way you play that idol and critic you saying that he/she does not act that way in real life... >.> has if they new better. -sighs-

Here and example of and AU rp with original chara not idols.
EXAMPLE

Writer 1: Alice smiled to Nick, waving her hand at him. He seemed tired this morning did he stayed all night watching anime again?

Writer 2: Seeing his friends waving her hand, the male did the same and smiled back. "Good morning..." he said keeping himself from yawning. He shouldn't have finished the whole season of Tokyo ghoul in one night.

Some people do it that way. Either some extra long para or simple lines like that. As it goes on, things happen and the characters lives on plots that both writers decided before hand together. It can be /fully/ planned or half as in you simply know that they are friends and go in the same school and from that you go on to write a story. It is really like writing a fanfic but you do not control the other character's just yours. That way, there is always a surprise since you never know how the other will react.

This is how I and many other people roleplay

No idea tbh. Never done much research about this whoops.