Figure 1 is a histogram of weights for the crews in the 1992 Cambridge vs. Oxford boat race. The two outliers on the extreme left of the histogram are the two coxswains, one for each boat. Because of these individuals, the distribution of the data is skewed to the left.
Because the mean is not a robust estimator, the presence of these outliers decreases the value of the mean weight. The mean of all the crewmen in the race is 181.4 pounds. If we exclude the coxswains from the data, then the mean weight increases to 190.4 pounds.
The median is a robust estimator of location. It's value does not change greatly when extreme observations are excluded. The median weight of both crews is 185.5 pounds. If we excluded the coxswains, then the median weight is 186 pounds.
This shows that the mean is greatly influenced by extreme values in the data, while the median is hardly affected at all.