What is the difference between App-V, VDI, and MED-V? They're all virtualization technologies of one kind or another, but how are they different?
App-V "streams" an application from a server to a client. The processing and resource usage happens on the client. This is basically the reverse of RemoteApp, if you're familiar with Remote Desktop Services.
VDI is when you present virtual machines to each of your users that they normally access through a thin client and RDP. They get virtual desktops that are typically spawned from the same base image, so that updating and configuration across the desktop fleet only happens once. It also removes the need for desktop hardware upgrades. You just need to keep your virtualization backend up to snuff, not a whole fleet of client PCs.
MED-V basically adds a management layer on top of the Virtual PC based XP Mode. It allows for full desktop virtualization of XP on a later OS for legacy application compatibility. MED-V allows for easier management of these per-desktop VMs.
As you can see, they're all very different things that solve different problems.