Middle Earth was a confounding, massive place. That’s one of the things that appealed to people about it. JRRRRRRRRR Tolkien created an amazing, huge world entirely from his imagination. Heck, he even made real languages for the people. The scope and scale of Middle Earth goes well beyond the four books you are familiar with. Tolkien even wrote a billion page novel about the history and lineage of all that shit, called The Silmarillion.
You could read that billion page book, which I doubt you even own, or you could watch this very thorough four-minute video which pretty much sums it all up.
I watched and learned some cool shit. Like did you know orcs were once elves? No. Freaking. Way. I would have never guessed that.