Our world is a wonderful, complex place that takes people lifetimes of study to understand. Even so, these people who do devote their lives to understanding our world often come up with more questions than answers.
Obviously, all stack exchange sites are a limited format. We cannot give a lifetime of expertise in such a short space. We will have to use terms and ideas to summarize worlds. Just like our world, there will be different aspects or areas of interest, and just like in the real world, one area of interest can affect another.
Therefore, I submit that we need a common vocabulary to talk about worlds.
The intent of a world-building vocabulary is to increase people's ability to effectively communicate what is going on. How do we know if a world shares the same physical principles and properties as our own? Do we just make assumptions? Should we talk about worlds according to a genres of games or books they appear in? How can we describe worlds in a short and effective way?
For example, assume the world from the Tolkien's Lord of the Rings was unknown to all but one person. That individual comes to our site for help. Can we have a common vocabulary so this person can say "classic fantasy world" instead of "a world based on Middle Age Europe with subtle or low magical elements whose physical properties closely approximates our own"?