Measure of Central Tendency

What is a measure of central tendency and what are the common measures of central tendency? Also when is the median preferred over the mean?

A measure of central tendency is the single numerical value considered most typical of the values of a quantitative variable. The most common measures of central tendency are the mode (i.e., the most frequently occurring number), the median (i.e., the middle point or fiftieth percentile), and the mean (i.e., the arithmetic average).

Median is preferred over the mean when the numbers are highly skewed (i.e., non-normally distributed).