- X on Wayland: an X client which talks with a special X server (XWayland) which itself will use Weston as its backend and then Weston will send the data to its own backend.
- "Wayland" on X: Weston has an X backend, which means that instead of discussing directly with the hardware, Weston can send its buffers to an X server which will talk with the hardware.
This was mostly useful when developping Weston..
Also your clarifications about Wayland was a bit incorrect, Wayland is:
- the name of the project
- the name of a protocol
- the name of a library which implement this protocol.
Overloading is bad for communication, so I prefer to talk about the Wayland Foo (Foo=project, developers, protocol, library) than Wayland alone.