Contraceptive gel is a form of birth control that looks like hair gel. It is not as common as oral contraceptives like birth control pills, contraceptive injections like Depo Provera or condoms, but still available. If you are concerned about preventing pregnancy and for some reason don't want to go a more traditional route, maybe contraceptive gel is for you.
Contraceptive gel is nonoxynol-9 in gel form. Nonoxynol-9 is a spermicide. It works by killing sperm so your girl can't get pregnant. This is exactly the same thing as contraceptive foams, creams, films and suppositories. The gel was invented in response to complaints that the foam was too messy. The gel is a bit thicker and more likely to stay where you apply it.
Contraceptive gel goes inside your girlfriend. You don't rub contraceptive gel all over yourself, you insert it into her. Once inside her, it will hopefully do its work killing your errant sperm.
Contraceptive gel isn't very effective alone. It's meant to be used along with a cervical cap or sponge or a condom. If functions more as extra insurance than an actual birth control method.
Contraceptive gel irritates a lot of people. Not just because it's messy and it stinks; contraceptive gel may literally irritate your skin. Try testing it out on a small patch before you start slathering it around. Do not attempt oral sex with contraceptive gel. Neither you nor she should eat this product. Also, contraceptive gel won't protect you from STDs. Use a condom for that.