The idea
The mean is the total divided by the number of observations; the median is the middle ordered value, or the mean of the two middle values for an even count. Extreme observations can move the mean substantially. Always consider spread and the sample size as well as a single center value, and do not discard an outlier simply because it is inconvenient.
Worked example
For five fictional delivery times of 2, 3, 3, 4 and 18 days, the mean is 6 days and the median is 3 days. The 18-day observation deserves investigation, but excluding it needs a documented reason. Reporting only the median would also hide the long delay experienced by one customer.
Try it
Calculate the mean, median and range of 4, 5, 5, 6 and 20 minutes. Then calculate the mean without 20 and describe what changed. Write a two-sentence summary that includes the sample size and the unusually long wait without assuming it is an error.