The PROGRESSBAR element provides a way to display progress information in a horizontal or vertical control. This element is identical to the SLIDER element. A progress bar is normally a slider that is not interactive, but there is nothing that prevents it from being used interactively. This element is provided solely as a convenience tag for making the noninteractivity clear in your code, if you choose to use it that way. It has no other value.

Skin Programming Reference

SLIDER Element