A Google Earth Pro license key is a unique code that is required to begin using Google Earth Pro. A license key is issued to the purchaser at the time of payment. A license key is not required to use the free version of Google Earth.
Google Earth Pro is a premium service that offers all the basic features as the free version of Google Earth, plus additional capabilities that are designed for business and advanced level users. A few examples of the expanded features in Google Earth Pro include the ability to import GIS data, create premium movies, map multiple points simultaneously and a map-making tool.