I think it goes like this.
The
Username is the name of your account. That's technical. I guess the database uses it to know you are you.
The
Name is as it says below,
This is the displayed name that people will see, so that's the part you want to change.
You can't change your account name, but you can change the alias of your account. So if you don't want to use the 'always stay logged in' then yes, you have to type in GuiltyRoachKillar every time you come to visit us, but if you change the account alias as GRK we'll know you as GRK.
Hope that's accurate enough and makes sense