The Mean is the average value for a set of observations. It is found by adding all the observations in a set then dividing by the number of observations in the set.
The Median is the middle observation in a set of observations. It is found by first arranging a set of observations from smallest to largest then getting the middle observations. If a set has an uneven number of observations, the median is just the middle value. If the set has an even number of observations, the median is the average of the two middle observations.
The Mode is the observation that frequently occurs in a set.