Plotting points in three-dimensional space can be difficult when limited by the two dimensions of a piece of paper. However, the concept is roughly the same as it is for plotting points in two dimensions. In 3D, the x-axis and y-axis measure horizontal distance left, right, up, or down along the flat plane that is, say, the top of your desk. The z-axis runs vertically through that plane (imagine poking a stick through your paper straight through the origin); it measures vertical distance above or below the plane on which the x- and y-axes lie. Points are plotted in the form (x, y, z). The graphing process can be difficult to understand from a written description, but the link below should help. It is a 3-D point plotter that shows what the three-dimensional coordinate plane looks like and helps you plot the points.