Hemorrhoids are enlarged veins in anal area, they look like a pinkish/bluish clumps of mucosa. You can see and feel external hemorrhoids. They may be painfull, like after prolonged sitting, they often itch, and often bleed when you strain. Internal hemorrhoids are not seen from outside, are usually not painfull, but can cause thin stools. They can be detected by doctor during rectal examination. Small amount of mucus may be present in stool.