My Free Backgrounds
Backgrounds are the image or images that create part of your scenery that form the setting of your object Sprites.
Generally not something you interact with as a player, but necessary in most cases as they can bring 'Atmosphere' to your level environments and give an impression of perspective to your games.
They come in 2 different forms that I Know of depending on your chosen genre of game.
1) 'Static' backgrounds don't move and are fixed, common in 8 bit games and 'Side Scrolling' games. (Mario Bros 3)
2) 'Parallax' backgrounds are multi layered, moving at different speeds and directions which can simulate distances and speeds. (Sonic the hedgehog)