Games require a screen of some sort. In the case of normal consoles, a television is the most common form of screen used. The screen is used as a source of visual output. As the player pushes buttons and moves analogs on the controller, the screen responds to the actions and changes take place on the screen, simulating actual movement.
Consoles use a large sized (albeit low-resolution) television as their visual output device: optimal for viewing at a greater distance by a larger audience. As a result, many video games are designed for local multiplayer play, with all players viewing the same TV set, with the screen divided into several sections and each player using a different controller.
Video games have generally had access to less computing power, less flexible computing power, and lower resolution displays. Dedicated consoles were advanced graphically, especially in animation. This is because video game consoles had dedicated graphics hardware, were able to load data instantly from ROM, and a low resolution output would look better on a television because it naturally blurs the pixels.