A beetle, for example, has a hard external skeleton, to which everything else is attached. A cat, for example, has a hard internal skeleton, to which everything else is attached. A cat is soft outside (although with teeth and claws) while a beetle is soft inside.
This is not a new idea. The famous Model-View-Controller design pattern requires three independent but linked components. And to my way of thinking, the Model is like the skeleton.
Whether or not you like the analogy, you can ask this: Does my application have a major component that can function relying on HTML and the DOM? My view is that for complex things this is the way to go, rather than hanging everything on the DOM.
Here’s another analogy. A modern web framework, such as Django or Rails, has something like a skeleton, and then templates can be used to add presentational logic and preferences. This is so different from the old CGI-script way of doing these things.
With a modern web-framework, generating the HTML is an important but external task. The generated HTML is like the soft skin of an animal. (Yes, even the rhinoceros has soft skin, although not like a baby.) The web-framework helps provide a good part of the skeleton.