Hemorrhoids are swollen veins in the anal canal. This common problem can be painful, but it's usually not serious. Veins can swell inside the anal canal to form internal hemorrhoids. Or they can swell near the opening of the anus to form external hemorrhoids. You can have both types at the same time. The symptoms and treatment depend on which type you have. Hemorrhoids are swollen veins in the anal canal. This common problem can be painful, but it's usually not serious. Veins can swell inside the anal canal to form internal hemorrhoids. Or they can swell near the opening of the anus to form external hemorrhoids. You can have both types at the same time. The symptoms and treatment depend on which type you have.