Which form of prevention also prevents sexually transmitted infections?

Explanation

A condom is a rubber barrier device put on a man's erect penis to block ejaculated semen. Unlike other forms of prevention, it prevents both unwanted pregnancy and sexually transmitted infections. The first condoms were made out of woven material, but were not very effective. Later came condoms made out of lamb intestines, which can still be bought today and are used e.g. by people suffering from latex allergies. Many condoms are also lubricated.