Close-up of an unrolled condom or sheath, showing the small teat for holding semen. Assorted condoms, in their protective wrappers, are seen at bottom. A condom is a male contraceptive in the form of a sheath which is fitted over the penis before sexual intercourse. The device prevents sperm from entering the vagina & possibly causing a pregnancy. The condom is also a prophylactic against venereal disease, & more recently, against the HIV virus, which is the cause of AIDS (Acquired Immune Deficiency Syndrome).