Zero dimensional refers to a point since a point has no dimension. In other words, a point has no length, width, height, or depth.
The origin with coordinates (0,0) in the coordinate system is a zero-dimensional point.
Note that we cannot draw the picture of point since to draw something you need dimension(s) such as the height, the length, the width, the depth, or a combination of these.
However, you can have a graphical representation of a point by using a dot or a small mark.