Parallax scrolling is a web site trend where the background content (i.e. an image) is moved at a different speed than the foreground content while scrolling. Click on the links below to see the difference between a website with and without parallax scrolling.
Parallax scrolling does not always work on mobile devices/smart phones. However, you can use media queries to turn off the effect on mobile devices (see last example on this page).
Use a container element and add a background image to the container with a specific height. Then use the background-attachment: fixed to create the actual parallax effect. The other background properties are used to center and scale the image perfectly.
Some mobile devices have a problem with background-attachment: fixed. However, you can use media queries to turn off the parallax effect for mobile devices