A page's address is what every link to it points at — search results, old emails, other people's sites, somebody's bookmark. Rename the page and all of those stop working on the same afternoon.
A redirect says "that address moved here", so anybody following an old link still arrives. A permanent one also tells search engines to move what the old address had earned across to the new one.
Still stuck? Ask the developers who wrote it. We aim to reply within one business day.
