Can someone please explain what user flairs are for?

The newbie's guide to Reddit already answered my questions on how to gain karma, how to post, and how to comment. Nevertheless, I'm still confused on the purpose of user flairs. I can understand the purpose of post flairs because they're like little tags that indicate whether a post is a meme or a discussion. But user flairs? What are they??? I don't know if that is a silly question but I figured it wouldn't hurt to ask here.