Parallax Scrolling for Web
This has been around for a little while, but worth mention:
The parallax effect, also called parallax scrolling, is a special technique used in computer graphics at first, where background images move by the camera slower than foreground images. This is the actual concept where websites with parallax scrolling started. It was widely used in the gaming industry more than 10-15 years ago and it is still used today in different domains.
In the past years the parallax effect started to be used widely in web design. Its popularity went through the clouds when Nike redesigned their website based on this concept. Their example can be seen in the showcase below the conclusion.
The design concept started to be used because it is actually quite cool. It looks good, it is (still) an original choice and is very successful as well. The effect makes different elements on the page move at different speeds. The background usually changes by scrolling, but it is not always the case. At its best, the parallax scrolling features various layers of images which are stacked on top of each other, with all of them moving at different pace to create a 3D effect out of 2D elements.