Common warts are small, grainy skin growths that occur most often on your fingers or hands. Rough to the touch, common warts also often feature a pattern of tiny black dots, which are small, clotted blood vessels.
Common warts are caused by a virus and are transmitted by touch. It can take a wart as long as two to six months to develop after your skin has been exposed to the virus. Common warts are usually harmless and eventually disappear on their own. But many people choose to remove them because they find them bothersome or embarrassing.
Cited from the Mayo Clinic & the American Academy of Dermatology