What the heck are all those terms – PV, HVM, HVM with PV drivers, PVHVM, PVH?

If you have to deal with Xen from time to time and not on a permanent basis and want to refresh the difference between all those Xen modes, I strongly encourage everyone to read the following two outstanding articles:

The Paravirtualization Spectrum, part 1: The Ends of the Spectrum
The Paravirtualization Spectrum, Part 2: From poles to a spectrum