If you have acne, you're likely to have zits: little raised areas of your skin that are usually filled with pus. Your doctor will call those little bumps pimples, but many people call them zits, which is an informal, slangy word. Teenagers tend to get a lot of zits: it's one of the difficult parts of adolescence. It seems like a new zit always pops up at the worst possible time, like right before prom.