There are many different types of birth control and they all fall into two different categories: Barrier and Hormonal.

Barrier Methods basically block the sperm from getting to the egg.  Some examples are condoms (male and female), diaphragms and cervical caps.

Hormonal Methods change the scheduled period of a woman to prevent the release of an egg from her ovaries, known as ovulation. That makes it nearly impossible for a pregnancy to happen.  Some examples are birth control pills (the Pill), Depo-Provera (the shot), and the birth control patch (Ortho Evra).