I'm still not entirely sure what GMod Tower is exactly, but Im also too scared to ask what it is without expecting to be attacked about why I even posted here.
So anyways, thats some good news. Hope its good.
GMod Tower is a social gamemode for Garry's Mod. Think something around the names like Club Penguin or Virtual Magic Kingdom.
You can play around 5-6 gamemodes in one gamemode. That sentence does sound odd, though.
You can get your own suite, decorate it, invite some friends over, or have a party.
There are store where you can customize yourself and get items for your suite.