there's this one grill on YT whose vids i like made a video about it, 6 minutes into the vid she still hadn't even begun to touch on what it means so i bailed.
The death of the author, is a tool in literary criticism (also applied to other media) that postulates that the personal beliefs, background and statements by the author don't pose any higher authority when analysing the themes of a work.
This means, for example, that even if the author was an evangelical christian and he set out to do a book that reflects that, it doesn't make any alternative readings any less valid as the text has a life of it's own.