Yeah, it was also kind of crazy that the three people who picked 7 were all almost in a group.

Mean is the kind of average people usually mean when they use the word 'average': you add up all the numbers, then divide by the number of numbers.

Median is a little more simple-minded: you list all the numbers in order from lowest to highest, then pick the one in the middle. (If there's an even number of numbers, so there isn't a single number in the middle, then you take the average of the two numbers in the middle.)