The mode is a measure of center. It's the score that occurs most often.
Mode can be used for nominal variables (that's not true for Mean and Median).
Graphically, the peak of a histogram is the mode.
- for a (discrete|nominal) random variable means the majority value. (ie the value with highest probability (the location at which the probability mass function has its peak);
- for a continuous random variable, the location at which the probability density function has its peak.