The part about negotiation is a bit off-track.

On one end, in the kernel, there’s a big array of pixels that is a picture that gets drawn on your monitor (or monitors). On the other end are a bunch of programs that want to draw stuff, like pictures of your friends and web pages. In between is software that decides how the stuff the softwares want to draw get put into the pixel array. This is Wayland; it was written to replace Xorg, which is what did that job for decades prior to Wayland.

If you understand the concepts of Xorg and window managers, Wayland + a compositor = Xorg + a window manager. Wayland abdicated a lot of work to the compositors, making it simpler and easier to maintain (and compositors more complex and harder). But together, they all do basically the same job. If one of the compositors implemented a network protocol, then you could declare equivalency.