The video tutorial about CSS position by Chris Coyier from Css-Tricks. This tutorial will show you the overview of CSS position values, if you’re new to CSS or want to learn more about this topic I think this video is right for you.
This is a quick beginner-level overview of the different CSS position values. In a nutshell: relative allows you to “nudge” and leaves the element’s original position in the page flow. Absolute and fixed allow for exact placement of elements and remove them from the page flow. Fixed positioned elements are unaffected by scrolling. All of them set a new positioning context and allow z-index to work.