Ovulation is when a mature egg is released from the ovary, moves down the fallopian tube, and is available in the fallopian tube to be fertilised.
Day one is the first day of the menstrual period and the last day is the day before the next period begins.
Ovulation happens about two weeks before the next expected period. So if your average menstrual cycle is 28 days, you ovulate around day 14, and the most fertile days are days 12, 13, 14 and 15. This will vary as per the cycle length of the patient.
In order to try for a natural conception, a doctor will advise to have intercourse on the most fertile days.
In case of monitored cycle, ovulation is tracked through regular sonography wherein in addition to follicle growth, thickness of endometrium and condition of uterus is also monitored.