What is a 'Leap Year'

=> The month 'February' consists of both number of 28 days & 29 days.
This February month consists of 29 days only when the Year number is equally divided by 4(four) and its called a Leap Year.Exp: 2000,2004,2008,2012 these are Leap years.

=> Actually the Earth needs exactly 365 days 5 hours  48 mins 46 seconds to make a full revolution. So the Extra 5 hours 48 mis 46 sec are counted after each 4 years as a complete day.And this day makes a Leap Year.And Leap years comes after each 4 years.