"A cache is like a smart librarian. When a patron asks for a Harry Potter book, the librarian goes looking for it on the shelves (i.e., the hard drive) and comes back with it along with the other Harry Potter books that were filed around it. This material is kept in a special place behind the desk (cache memory) so that when other patrons ask for a Harry Potter book, the librarian can retrieve it much more quickly. It's an efficient system indeed."