Consider the x-y axis. The x-y- axis is the whole plane, it contains the set of all possible pairs (x, y), where x and y are real numbers.
The set y ≤ 5, includes all those points (x, y) in the plane whose y coordinate is less than or equal to 5. Thus, x can be any number, but y has the restriction
of being at most 5.
According to this discussion, the graph is as in the picture attached. We color the horizontal line y=5, and all points below it.
