how does the birth control pill prevent pregnancy?

Answer 1

simply put, birth control pills contain a hormone that fools your body into thinking you are pregnant- since your body thinks you are pregnant you don't ovulate- no eggs to fertilize, no babies.

Answer 2

Birth control pills contain a synthetic version of the hormone progesterone. In the case of the combination pill, they also contain a synthetic estrogen. Progesterone is released in large quantities when a woman is pregnant. It inhibits ovulation, thickens the cervical mucus and builds up the uterine lining.

Answer 3

The above are correct but there is ALWAYS that 1% chance that you can get pregnant on the pill.

Pills are only 99% (like most other contraceptives).