The mode is what items or numbers appear most often in a set.
Example 1: Consider the following set: 2, 4, 5, 5, 7.
The number that appears most often is 5. Hence, it is the mode.
Example 2: Consider another set: 1,1,1,2,2,3,4,4,4,4.
As, 4 appears most often. Hence it is the mode.