The median is the value of the "middle number" of the sorted data set; by definition, half of the values are above the median, and half are below

if there are 101 data points, the median is the value of sorted item number 51 (50 are below it and 50 are above).

The median is also the 50th percentile.

The median of the set (1,2,3,4,5,6,7,8,9) is obviously 5

The key to finding the median is sorting the set. (The median of the set is not so obvious when not sorted: (8,5,6,1,2,7,4,9,3).)