> Then what're Weston and QTWayland?
Weston is a _compositor_. I.e. it's something like a WM in X world. And QTWayland is simply a name of QT integration with Wayland.
> I still don't understand what you mean.
Basically, Wayland provides a way for processes to communicate using a special form of IPC. Applications can use this IPC to exchange any type of data they want. Wayland itself also provides some services (described in wayland.xml) using this IPC.
> It's like saying that you can use GIF to store MP3 data just because you can put mp3-file to the directory with gif-files.
No. I'm saying that I can use Dropbox to synchronize not only Dropbox user manual but also GIFs and MP3.