HPV (human papillomavirus)is the virus that causes genital warts, but there are over 100 strains and not all human papillomaviruses cause visible signs. The virus infects mucous membranes and skin, such as the vagina, cervix, penis and rectum. it is an extremely common STD and most sexually active individuals contract HPV at some time, although depending on the strain may or may not know they have it.

The following sources provide excellent information about this infection:

Centers for Disease Control

MedlinePlus

Food and Drug Administration 

American Sexual Health Association

Smartersex.org 

Gardasil

Women's Health.gov

Gay Men's Health