Starting with AutoCAD 2010, the old Portable License Utility (PLU) has been replaced by the License Transfer Utility (LTU). The old PLU essentially created a "license file" that you could move from one computer to another using a network, flash drive or any other method. If you bought a new computer for example, you could install AutoCAD on the new computer, and use the PLU to transfer the activation from the old machine to the new one.
The only problem with this is that the PLU failure rate was about 50%, and because you had to define the target machine when you exported, you could not re-import back onto the same machine.
So along comes the LTU. So what is the difference? The LTU copies your activation up to the Autodesk servers where it can sit until you are ready to import it. So far in my testing, it has not failed once. Of course you will need an internet connection on both machines, and you will need an Autodesk UserID and password. If you don't have one, you can create one.