For a skewed distribution, then the tail is longer to one side from the center than to the other. In a right skewed distribution, the tail is longer to the right.
When a distribution is skewed, the mean will be closer to the tail Than the median. Therefore. For a right skewed histogram, the mean is closer to the tail of the histogram and hence closer to the right. Once this happens, values closer to the right of a distribution are higher (number line). Thus the mean will be greater than the median.