A Condom or a rubber is a device used during sexual intercourse for two major purposes - 1. Contraception and 2. Preventing the spread of Sexually Transmitted Diseases (STDs).
It is streatchable sheath made of latex which is worn by the man on his penis before he has sex with his partner.
Though condoms started as a way for men to prevent their partners from becoming pregnant, today this useful innovation is not only available for females as a Female Condom, but is also used for purposes other than pregnancy prevention (like safe sex).