This video show how to use Object Tracking in AutoCAD.
To use Object Tracking, you need to have your Osnaps active (Press F3 to toggle them on and off).
Object tracking is a great way to quickly place new objects using Osnaps as a starting point.
It is also a way to ruin your drawing by having sloppy habits. You need to be care and pay attention when using these tools. Use this tool in conjunction with Direct Distance Entry to speed up your CAD work.