What's different between OpenVZ and XEN?

I've read some articles, i know 3 types of VPS:
- OpenVZ
- Xen
- WMWare

As i know. OpenVZ support only VPS Linux, Xen support VPS Windows (maybe also linux)...I'm gonna going sell VPS (only Windows) and i wanna know how to create VPS on DS.

Besides, my friends sell VPS and i see some informations:
- 1 CPU
- 1 IP
What's does it mean?

Thank for reading and have a nice day :)