Okay, I'm a complete noob. So there's that.

What are guilds? Clans? What exactly does belonging to one of these entail? Is there a difference?

All clans are a little different, and a guild is basically the same thing as a clan. Anyway, some clans are a group of friends playing together, some only accept the best players, and some focus on role playing. The benefit is you have people you can play in team games that you have played with before (and hopefully you know they won't get booted). Clans can also add fun to the game in different ways like ranks or custom ladders. Anyway, hopefully that helps you.

Thanks. A player in an open game mentioned that we are in the same guild... I had no idea I was in a guild. How do I find out if I am / what that guild is?

I'm just as confused about that other player's remarks as you are. Shrug.

You are not currently in a warlight clan, as you lack the flair. For a list of all the warlight clans go to http://warlight.net/Clans/List