Challenge 1 -- what does createsSortDescripter do?


I’ve just finished Challenge 1. I couldn’t get it to work until I read viewtopic.php?f=180&t=3648 and saw that one thing you could try was to check/uncheck “createsSortDescriptor” in the Value binding of the NSArrayController. I unchecked it, and that worked. But I don’t understand what that did or why it mattered. Can anybody help?