Mean: The "average" number; found by adding all data points and dividing by the number of data points.
Example: The mean of 4, 1, & 7 is (4+1+7)/3 = 12/3= 4
Median: The middle number; found by ordering all data points and picking out the one in the middle (or if there are two middle numbers, taking the mean of those two numbers).
Example: The median of 4, 1, & 7 is 4 bc when the numbers are put in order (1, 4, 7), the number 4 is in the middle.