ANSWER: Moles are groups of pigment cells, and nearly everyone has them. Most moles are harmless, but it's possible for melanoma — a rare but serious skin cancer — to develop in or near a mole. Although it may not be serious, a mole that bleeds is a possible sign of melanoma. More @Wikipedia
Hover over any link to get a description of the article. Please note that search keywords are sometimes hidden within the full article and don't appear in the description or title.