Ovulation is the monthly release of an egg from a woman's ovary into the fallopian tube. If the egg is not fertilised by male sperm (which happens because of sex) then the egg is released from the body along with uterus lining as a menstrual period. Ovulation usually occurs 14 days before the start of the next menstrual bleed but each woman's cycle is different and a woman's cycle can change month to month.
Attribution: Straight Talk Foundation