The feature is essentially a website plugin: visitors to Buick.com or GMC.com can choose a vehicle, configure it to their hearts' content, then use a Facebook Connect-style API to save the vehicle to their Facebook profiles. Saved vehicles can be viewed by friends and, of course, "liked".
The idea behind the development is to allow shoppers access to the one tool everyone relies on: the opinions of family and friends. As U.S. vice president for GMC marketing John Schwegman said, "We recognize that car buyers are not only looking for product information when shopping for their next car or truck but also use feedback from friends and family to help narrow down their selection."
If you've spent any time online, the Facebook-sharing feature should look and feel familiar: it's simple, intuitive, and very similar to sharing features from other websites. But just in case you'd like an overview, here's a quick video explaining how it all works: