I know that $3$-D graphs are in three dimensions $(x,y,z)$, but I also know that it is possible to draw $4$-D graphs. After googling it, it looks like a slightly more complex $3$-D graph to me. Can someone tell me the difference?
EDIT: The hypervolume, ex. a hypercube is in $4$-D
You want to convey information in higher dimensions on a $2D$ screen. What is generally used for $3D$, is a projection of a two dimensional surface, where $z$ is a function of $x,y$ . For $4D$ color is generally added, so that in addition to height, a color is used to represent the value in the fourth dimension. Other methods used include drawing multiple "$3D$" graphs, each for a different value.