2D images are defined as having height and width. In digital images the width of an image is defined by the "x" axis and the height by the "y" axis.
When describing image resolution we always state the width followed by the height. For example a high definition TV screen would be 1920 x 1080px.
In the early days of video games nearly all games were exclusively 2D.
This was mainly due to the limitations of the available hardware.
3D images have height, width and depth. The depth information is defined by the "z" axis.
Early 3D images were quite primitive, with little detail and no shading. As the technology improved, 3D graphics became more advanced.
Today 3D images can be seen in many forms from big budget movies such as Avatar and Toy Story to television adverts for products such as toilet duck.
Video games have also progressed to the point where the majority of big budget titles feature 3D graphics.
The next big development in 3D graphics is likely to be the use of glasses to produce stereoscopic 3D images.
