A quartile is a value which divides the data into four equal parts. It can be any of the three values which divides the data. The first quartile is known Q1 or lower quartile and it cuts off lowest 25% of the data. The second quartile is Q2 or median which cuts off set in half. The third quartile is known as Q3 or upper quartile and it cuts off highest 25% of data. Moreover, the difference between the upper and lower quartiles is termed as interquartile range.