They reduce menstrual blood loss and a woman's risk for anemia. Acne often improves. Many women enjoy sex more when on pills because they know they are less likely to get pregnant. Use condoms to protect yourself from STD's. You have to remember to take the pill every day, at the same time.
Pills tend to make periods very short and scanty.
You may see no blood at all. Most women like this when they understand it is normal. Taking the pill may cause headaches, depression or decreased enjoyment of sex in some women. A backup contraceptive is required for 2 weeks if you have any question about how many pills you have missed and whether a backup is necessary.