Mean (Average) - If you made all values identical, what would you have to pick so that the total remains the same? This is the average.
Median - Pick the value from the set that's in the middle when you put them in order. The median is the value that has the same number of things greater and less than its own value.
Mode - what happens the most? Pick the value that happens more times than any other value. Sometimes, there is no mode.