It's what you're in right now. 3nodding
It's like a little hangout place to go and talk to people who are members in the guild.
Some guilds have themes and some don't. Like there are guilds that are themed for Kingdom Hearts fans or Sports fan, etc. Some guilds don't really have a theme and you can talk about anything as long as it's not against Gaia's rules. (Meaning nothing too graphic, no bad pictures, etc.)