The mode is simply the number which appears most often in a set/array.
It must have a frequency of 2 or greater and there can be multiple modes.
Here are examples!
Find the mode of a set.
Set = {1,2,3}
Number of modes = 0, Frequency = 1, Mode set ={null}
Set = {1,2,3,1}
Number of modes = 1, Frequency = 2, Mode set = {1}
Set = {1,2,3,1,2,3,1,2,3}