When you start the network version of an Autodesk product, a request is made to the network for a license. The Network License Manager controls the licenses that are issued and handles license requests through feature codes. Feature codes are specific to the networked application.
Product keys are required for installation of Autodesk products and are used to differentiate products that are both sold independently and as part of a product suite. The same version of AutoCAD is in both software packages, but the product key differentiates one package from the other.