Hemorrhoids are swollen and inflamed veins that appear on the anus and lower rectum. They are also known as piles. Hemorrhoids often occur when a person strains during bowel movements or is constipated, or when women experiences increased pressure on the veins during pregnancy. Hemorrhoids can be internal or external. They may appear inside the rectum (internal) or under the skin around the anus (external). Both types of hemorrhoids can cause anal pain, bleeding, itching, or a hard lump near the anus.