Update July 2018: Citrix are finally returning to non-idiotic product names.
I believe Citrix too are confused when it comes to their product range. For a few years now every product they have is named “Xen[something]”.
I am trying to explain to myself which product is which.
It all started with Citrix’ original product “Metaframe”, a stateless seamless graphic terminal protocol, i.e. something like X11 but applications continue running on the server when the client disconnects and will display again when the client reconnetcs. Metaframe is now a “Xen[something]” product, see below.
According to Wikipedia "Xen /ˈzɛn/ is a native (bare-metal) hypervisor providing services that allow multiple computer operating systems to execute on the same computer hardware concurrently”.
Citrix bought Xen in 2007 and used it as a basis for many of its own virtualisation products.
Xen is a type-1 hypervisor which supports two types of virtualisation for its guests, hardware-supported virtualisation, which requires a CPU with hardwar-virtualisation support, and ring compression with paravirtualisation, which requires modified guest operating systems. Like Microsoft Hyper-V, and unlike VMware ESX, Xen uses the first guest operating system as interface between other guests and hardware, i.e. it doesn’t require Xen-specific drivers but uses, usually, Linux drivers. Xen can also use specific driver guests that other guests can use.
Xen is today available in the form of infrastructure products from Citrix, Oracle and Novell as well as coming with many Linux distributions as an installable package.
XenApp is the renamed Metaframe explained above. It has nothing to do with the Xen hypervisor and runs on top of, generally, Microsoft Windows to extend Windows’ remote desktop protocol with better performance and more management features. XenApp apparently also supports “offline applications” if both server and client are Windows machines.
XenServer is Citrix’ commercial release of the Xen hypervisor. From what I can see it adds to the plain Xen hypervisor a Web-based configuration tool, a Windows-based configuration tool, and a Windows PowerShell module.
XenClient is a client-oriented version of XenServer with specific support for graphics hardware found in desktop and laptop computers and direct access to such hardware for the VMs.
XenDesktop appears to be a combination of XenClient and XenApp to allow users access to their “desktops” (i.e. VMs) and applications running on Xen/Hyper-V/ESX servers (VMs) or Windows servers (applications). Using a local type-2 hypervisor and XenApp XenDesktop can either display or run a VM and if running on Windows it can also run Windows applications from the server “offline”, i.e. when the server is no longer connected.
I have no idea what this is and the homepage could not explain it to me either. I am guessing it’s either XenApp or XenDesktop, both without offline mode, for mobile devices. But it could be anything. According to Citrix’ documentation XenMobile is a "comprehensive solution to manage mobile devices, apps and data”, whatever that means.