People born on Feb 29 are called Leaplings.
Applies to the Gregorian Calendar.
Leap years were initiated by Julius Cesar.
Earth’s orbit around the sun is approximately 365.2425 days.
To bring calendar in line with actual time for earth’s orbit, a leap year is used for the correction.
If the year is divisible by four, one day is added every four years. There are exceptions; if the year is divisible by 100, then the added day is skipped and if the year is divisible by 400, then it is added.
February was chosen because it used to be the end of the year month. The year originally started with the vernal equinox (aka spring) and ended with February.