Help with Game Master

I haven't seen anywhere topic like this, sorry if I'm reposting.
What exactly is "Game Master"?
In theory, that's a user who can update Character Sheets. But if I put someone for Game Master, nothing changes. The user's still not able to update sheets. Or is it just for option "Dice roll"?

i guess its only for that dice roll option....

if a user decides to roll dice...

then under this users post appears a second post of that game master account.. where the actual dice roll happens

game master is the one who can edit the character sheet, also wheb you roll dice the message will be display under the game master name.



I am new to this RPG stuff, but I am developing one, http://play-by-post.forumotion.com