I don't know how technical you are but it looks likes this is a security token api to validate the trust of the environment. I believe that google is trying to propose a universal standard for everyone to use.
I think Firefox is standing negative because they want choice not 1 standard. This is the best I can do without going down a rabbit hole
Edit: link to another post
Truth, I haven't turned on my x since the first month and I don't know why we have it