musictheory.net is an excellent site, and buried distressingly far down this comment page. you can just click on the link and read for half an hour and you’ll

musictheory.net is an excellent site, and buried distressingly far down this comment page. you can just click on the link and read for half an hour and you’ll have more practical understanding than you’ll ever squeeze out of all of the comments here that purport to tell you the one critical concept that makes it all fit together. (or the ones that want to tell you how all the existing terminology is dumb and should be replaced. ugh.)