What is the difference between mean, median, and mode?

Mean (average): Add all values and divide by the count.
Example: {2, 4, 6, 8, 10} → Mean = 30/5 = 6

Median (middle value): Sort the data and pick the middle. If even count, average the two middle values.
Example: {3, 7, 9, 12, 15} → Median = 9

Mode (most frequent): The value that appears most often.
Example: {2, 3, 3, 5, 7} → Mode = 3

When to use which: Mean for symmetric data, median when there are outliers (like income data), mode for categorical data.