Two important aspects of a distribution are its centre and its spread.
The mean and median are descriptions of the 'centre' of a distribution. The mode is another description of a 'typical' value for discrete data.
The median is less sensitive to outliers and is easier to interpret than the mean. However there are more 'advanced' uses of means than medians.
The mean of discrete data does not need to be a whole number.
The median splits a data set into two. The quartiles split it into four, deciles into 10, and percentiles into 100.
The range in a data set is the difference between the maximum and minimum values. A better measure of spread is the difference between the upper and lower quartiles.
The mean absolute error and root mean square error summarise how close a data set is to a target, k.
The standard deviation describes how close the values are to the centre of the distribution.