CAD is a generic acronym for Computer Aided Design. It does not mean AutoCAD. AutoCAD is one product out of hundreds, all of which help you do CAD.
I use Pro/Engineer every day at work, another leading CAD program. Some others are SolidWorks, NX, and Catia. Most companies will invest in only one product as their bread and butter CAD program, sometimes buying a few licenses of others for specialty work. These programs are quite complicated and take years to become fully proficient with. I know senior engineers who have been using Pro/E their whole careers, since it came out, and they still learn new features constantly.
Honestly if you just have to make a quick model for your boss and this will not be your full time job, and you are not an engineer who needs the precision, try Google Sketchup. It is free, super easy to use, and you can get an OK model out of it.