If i remember right a simplified explanation would be: A protein is a long chain of amino-acids that folds into a specific structure to achieve a certain task(for example stuff like cut a certain bond in a certain molecule). Prion is the exact same chain of amino-acids but it has folded in a wrong configuration thus cannot complete the original function, and even worse it can refold other proteins with the same amino-acid chain to the prion configuration slowly spreading through the body infecting more and more proteins ultimately depriving the body of the ability to do a specific fuction

Pls someone correct me if im wrong because my source is a vague memory of likely a video i dont remember possibly years ago.