A plane figure is two-dimensional, and a solid figure is three-dimensional. This difference between the two is what gives modern graphics for films and video games a more realistic look.
The difference between plane and solid figures is in their dimensions. Where a square is a plane figure, its 3D counterpart, the cube, is a solid figure. The same comparison exists between a circle, or plane figure, and a sphere, a solid figure. Individuals create plane figures by connecting points on a grid to create 2D geometrical shapes. The same shape takes on extra dimension by adding additional points and lines to give the shape height, width and depth.