Simply put, it prevents you from getting pregnant. It works by keeping the ovaries from releasing eggs. It also contains hormone that thickens the cervical mucus, thus blocking bleeding after unprotected sex sperm and preventing pregnancy.
The morning after pill is taken within 3 days after the intercourse. There is, however, a newer version introduced in 2010 that lets you take it within a longer period, that is, within 5 days. It works best when taken within 12 hours of unprotected sex and is less effective as time passes. You can read more about that and other brands of emergency contraception in Emergency Contraception. Don’t take morning after pill if you’re already pregnant. A morning after pill is a kind of birth control, not abortion. It also does not prevent pregnancy for any unprotected intercourse that happens after taking the pill.
Expect to get your menstrual period within 3 weeks after taking the pill. If not, do a pregnancy test. Your menstrual may come a week earlier or a week later than normal. If it’s more than a week late, again, take a pregnancy test.