No, it is not virtualization. You are loading Windows on a real HD and using a real processor unlike a virtual system that uses a program to "trick" the system into thinking it is on its own machine. Basically bootcamp is nothing more than dual booting your machine.
The "Boot Camp Assistant" that is a non-destructive partitioning tool to create and remove Windows partitions
Firmware extensions that allow Windows to boot on the Mac (Mainly BIOS emulation since Macs are EFI based).
Drivers for Windows to support the Mac specific hardware.
Only the firmware extensions are really required. Only Windows 7 64 bit can natively boot from EFI and it often doesn't like the version of EFI that Macs use).