What are redirectors?

The “Fix Up Redirectors” action seems useless. Moreover, I seem to have to run that action after every file interaction: move, rename, create, delete. Even then, Unreal will leave “deleted” or “moved” assets on the file system, but hide them in the Content Browser. This is wasteful, annoying, and inconsistent. I don’t understand why “redirectors” are exposed to the average user. If they are filename/asset redirection to allow for filesystem abstraction and packaging management, great! But why should I know about them? Why do I need to clean them up all the time? Why do they cause more pain and anguish than simply having to fix some references when I move a file? Having an indication of the what the redirectors in my project are doing may help me to understand why they are useful and when best to utilize the “Fix Up Redirectors” action.