I just got invited to a guild. Why can't I see or talk in Guild Chat?

I just got invited to a Guild in Guild Wars 2. But after playing for a while, I noticed that Guild Chat was... unusually quiet. I know these people. They are chatterboxes. They normally do not shut up. So it seemed odd.

Then I tried to talk in /guild, figuring I'd kickstart some conversation. But I got an error message, informing me that "You Are Not In A Guild".

But that can't be right, because I can see my name on the roster! Why can't I talk in Guild Chat?

In order to participate in guild functions such as Chat, as well as to take advantage of various guild perks, and to contribute towards guild progression, you'll need to Represent that particular guild.

You can do this by pulling up the guild menu, and clicking the "Represent" button at the bottom of the screen. Additionally, while you can join multiple guilds, you can only represent one at a time, so you won't be able to participate in guild chat from multiple guilds simultaneously.