A condom is a thin, flexible sheath typically made of latex, polyurethane, or polyisoprene that is used during sexual intercourse to:Prevent pregnancy by blocking sperm from reaching an egg.Protect against sexually transmitted infections (STIs) like HIV, chlamydia, and gonorrhea.There are male condoms, which are worn over the penis, and female (internal) condoms, which are placed inside the vagina.[tex][/tex]