The mean is calculated by adding all values and dividing by the number of values. For example: the mean of 10, 20, and 30 is (10+20+30)/3 = 20.

The mean is the sum of all values divided by the count. The median is the middle value when all values are sorted. The mean is affected by outliers, the median is not.

The mode is used when you want to find the most common value in a dataset. It's especially useful for categorical data, like the most common shoe size in a group.