If you are new to AutoCAD, need a quick refresher or want to find out what it is all about, then the article below from Autodesk may be of use.
Welcome to The Hitchhikers Guide to AutoCAD - your guide to the basic 42 commands you need to create 2D drawings using modern AutoCAD or AutoCAD LT.
This guide is a great place to get started if you just completed your initial training, or to refresh your memory if you only use AutoCAD occasionally. As you can see from the illustration, the 42 commands are grouped together according to types of activity. In addition, these groups are arranged sequentially to follow a typical workflow.