Scrolling allows the user to navigate to content in the overflow using a swipe gesture. The scrolling speed is proportional to the speed of the gesture.
Appears during scrolling to indicate what portion of the content is currently in view.
In addition to traditional scrolling, a long alphabetical list can also offer index scrolling: a way to quickly navigate to the items that begin with a particular letter. With index scrolling, a scroll indicator appears even when the user isn't scrolling. Touching or dragging it causes the current letter to pop up in a prominent way.