출처: http://www.w3schools.com/css/css_image_sprites.asp

Image Sprites

An image sprite is a collection of images put into a single image.

A web page with many images can take a long time to load and generates multiple server requests.

Using image sprites will reduce the number of server requests and save bandwidth.

CSS Image Sprites

An image sprite
An image sprite - a navigation list
An image sprite with hover effect

Image sprites explained