What are the fundamental differences between OS X and macOS?

Question

macOS

Not in the know, but you need to find out, Google did not help, toaster help ..
Please add links to sources

Answer 1

There are no fundamental differences between them, only minor innovations, search the Internet and you will find.

Answer 2

Answer 3

In the title, right? Where did the idea come from that there are any fundamental differences between the two versions of the OS, one of which was simply renamed?

Answer 4

a trick question, most likely, you need to give an answer, but I'm not competent in the subject of apple.
Does that mean there are no differences?