A point is a location in space. In the context of math, a point is usually represented on a coordinate plane, by a set of ordered pairs:
The point plotted above is located at the coordinates (3, 5).
Below is another example of a point, this time, in an arbitrary space, denoted A, and represented by a dot:
Note that points are zero-dimensional, meaning that they do not occupy any space despite typically being represented by a tangible dot.
See also 0D.