The parallax effect has been around for years in classic video games, but it became a trend in the web design world. This cool effect is now commonly seen as part of the scrolling feature of a web page. It uses multiple backgrounds that seem to move at different speeds to create a sensation of depth (creating a faux-3D effect) and an interesting browsing experience.
Nearby objects have a larger parallax than more distant objects when observed from different positions, so parallax scrolling can be used to determine distances.
Scrolling Parallax Effect gives the design a sense of movement that wows the person who stops to see what your site offers. This one effect can compel a customer stay that you would have lost with just a static page of information. The movement to any design even the suttle is the holy grail to helping catch attention, so when you can add animation or movement you need to do so it becomes the natural stop sign you need to draw in potential customers.