I can't figure out the difference/relationship between menus and menus One of those fundamentals I skipped over because it gave me a headache to think about thinking about it:

Can someone explain, (or point me to documentation that can explain, and won't make me want to punch myself), the difference, the logic, relationships and/or whatever for "menus" (seemingly misnamed collection of page markers the things you make with HOOK_menu) versus "menus" (thingees that you click on to make events happen the things you make with menu_save())?

...bonus points if you can tell me why in the name of all things holy are log-in, log-out, register, my account, and hell, even "switch back" not built into a single core menu block so that I could continue to live in blissful ignorance...
hook_menu : Is used to define a path in Drupal. It also says what should be present in that path, who should have access to it and so.

Documentation of hook_menu

Menus : Is a list of links that fall under a category. For example Admin Menu(Admin Links), User Menu(Account, Logout) and Primary Menu(Home, Contact and so on)

Documentation of Menus