There are lots of different ways to prevent pregnancy, and the variety of methods are rarely covered in school, from what I hear. When I attended school, there was no sex education whatsoever. Later on, schools were caught up in "abstinence only" education, and today it varies from place to place at the whims of state and local politics. So I should not be surprised at how many people do not know the mechanics of how birth controls methods work, even if they use those methods. Minute Earth takes an overview of the most common modern birth control methods and explains what they do to interrupt the process of beginning a pregnancy. Here's the chart from the video.
Don't fret about the blurred-out side effect under vasectomies; that was an error that has been corrected. Also, people pointed out that a copper IUD is not a hormonal method; chemical would have been a better word. Whichever birth control method you choose to employ, you should read as much as you can about it. -via Geeks Are Sexy