I'm sorry.
Maybe I'm a little slow, but I don't understand this at all...
I have a:
Username
Name
Nickname
But I still want to use "GreenVirus," so do I have to fill in the nickname field? I uh... honestly don't get this...
I'll have three fields with the same information... :/
Username is for the purpose of logging in only. You and the admins are the only ones that will ever be able to see it. It should be different from your nickname.
Display name is what's on the top left of your posts and can be set to anything you want.
Nickname is the little line under your avatar that shows which user you are. It fills in for having to go to the user's profile and check the username there. As stated before, it should be different from your username for safety reasons.
So, for example, you can set your username to Jim Jim Jimmy Jim Jimmy Jim Jim, then set your nickname to GreenVirus, then set your display name to GreenVirus or whatever else you want. The purpose of having a different username is to make it significantly more difficult for someone to get into your account.