Parallel scrolling

In this tutorial, we have to see about parallel scrolling using javascript. What is parallel scrolling and where I used? For my prototyping tool, need this requirement of the parallel scrolling in timeline section. In the timeline, the section has two subsections left panel, right panel. the left panel has a list of elements with CSS properties, the right panel contains duration, easing, delay for each CSS property. If left panel scrolled, then need to scroll right panel automatically and vice-versa. Let see the simple script used in parallel scrolling.