Mode is defined as -
The mode

The mode is the value that occurs the most frequently in a data set.
For example the diastolic BP of 10 individuals 75, 71, 73, 84, 81, 75, 79, 75, 80, 90
The most frequently occurring value is 75, and therefore the mode.
If there are 2 most frequent value in the distribution, i.e., two modes → Bimodol distribution. 
For example: For Hodgkin's lymphoma, there are two age groups around which most of the cases occur.

Advantage

Easy to understand and is not affected by extreme items (skewed deviation).
The concept of mode makes sense for nominal data (i.e., not consisting numerical values). For example, taking a sample of korean family names, one might find "Kim" occurs more often than any other name. Then "Kim" might be called the mode of the sample.

Disadvantage

Exact location is often uncertain and is often not clearly defined.
Most frequent value
Middle value
Minimum value
None