Amazon offers HVM and PV operating system options for most instance types.
Para-Virtualization (PV) is means of virtualization support for best performance and stability.
Host and guest kernels should be attached.
1.The stability/Performance is close to the real servers and hardware virtualization.
2.Supports Linux only.
The "newer" option for virtualization is hardware-assisted virtual machine (HVM) whereby the host and guest kernels don't need to be attached.
It provides complete hardware isolation.
1.Resembles close to a physical server.
2.Can run Linux and Windows.