Traditionally, when you ordered a dedicated server, the operating system was installed directly onto the machine, similar to how a desktop machine would be have Windows or Linux installed.
Now, many we hosts are selling "smart servers" that have a visualization layer added. You still get 100% of the server's power and resources, but Linux or Windows is installed in a virtual machine instead of as the main OS. This has some benefits, such as being able to clone instances, keep snapshots of the virtual server as backups, and is generally easier to move to a new physical machine when the time comes.
Do you prefer a bare metal server, or a visualized one?