The document defines and provides examples to illustrate the median, which represents the middle-most value of a data set. The median is calculated by arranging the data points in ascending order and selecting the middle value for an odd number of points, or averaging the two middle values for an even number of points. The median is useful for summarizing large data sets with a single value and is less influenced by outliers than the mean. Examples are provided to demonstrate calculating the median for both discrete and grouped data.