Why it's done

If you use them correctly every time you have sex, male condoms are very effective at preventing pregnancy and the transmission of the human immunodeficiency virus (HIV), the virus that causes AIDS. Condoms also reduce the risk of infection from other STIs, such as gonorrhea and chlamydia.

Condoms don't have the side effects found in some forms of female contraception, such as birth control pills or shots, or potential complications of an intrauterine device (IUD). They're available without a prescription, so it's easy to have one on hand when you need it.