DevTools foundation is the core business logic of DevTools: mainly core/ and models/. The difference between “foundation” and the rest of DevTools is that the code is targeted not just for the browser, but also the Node.js runtime. As such, allowed use of APIs is restricted to what is available in both runtimes.
A DevToolsUniverse is a concrete, encapsulated instance of “foundation” scoped to a single root CDP target. It is valid to create multiple DevToolsUniverse instances simultaneously.