Sexually transmitted infections (STIs)—the name pretty much says it all…they are infections that you catch through sexual contact. There’s a lot of different ones and their treatment, symptoms, and severity depend on which STI you’re talking about. The bottom line, though? You don’t want to get any of these. The surest way to avoid STIs is to avoid having sex. If you are having sex, though, make sure you’re using birth control that protects against STIs each and every single time you have sex.