Emergency contraception

Emergency contraception is a form of contraception that can be taken by the woman after sex. Emergency contraception can not protect against sexually transmitted diseases. Emergency contraception may prevent a pregnancy. The drugs that are used for emergency contraception are based on hormones. 
Emergency contraception needs to be applied soon after the unprotected sex. If it is not applied within about 3 days (72 hours) after the event, it will no longer help to prevent pregnancy. The sooner the drug is taken after unprotected sex, the more effective it is.
The drugs work by either:
It is estimated that these drugs may prevent 85% of expected pregnancies.
The drugs will not work if the woman is already pregnant. The drugs will also not work for preventing pregnancy from unprotected sex again in the same menstrual cycle.
Often the drugs are available in pharmacies. In some countries, the affected person needs to talk to a healthcare professional (a doctor or a pharmacist). After this counseling, the drugs can be obtained.
Different from abortion.
Emergency contraception is not a form of abortion. Abortion is only possible when a pregnancy has started. This means that the ovum has been fertilized, and that it has attached itself to the lining of the womb. Contraception is about preventing a pregnancy. There are certain pills, for example those containing Mifepristone which are taken as a form of abortion.