Sometimes, people put buzzwords on their resume in the hopes that it will get them noticed. For me virtualization goes beyond just creating a virtual machine and running linux or windows on it.
Virtualization encompasses things like selecting hardware and configuring nodes (including failover) for the virtual environment. Deciding whether to use raw storage so that you can take advantage of a SAN solution that handles de-duplication or using virtual hard drives for portability. Creating a management portal and potentially a self-service portal for authorized users to automatically deploy virtual machines based off library templates.
In addition to server virtualization there is also desktop virtualization. This concept involves creating a farm of virtual hosts running desktop clients or a terminal solution and replacing desktop machines with thin clients. These clients typically cost less than $500 and don't have to be upgraded because the horsepower is all in the server.
Finally, there is app virtualization, where applications are stored in bundles. When a user needs to run the application, the bundle is deployed to the client machine and runs in an isolated environment.
If someone puts "Virtualization" on his resume, I'd expect him to be able to talk about one or more of these topics.