To redirect one page to another begin the first page with
where pagename is the final target page.
Extra text after the #REDIRECT command and link is ignored. It is rendered only in preview and in a diff.
If you move a page (basically, changing the article title), a redirect to the new title will automatically be created under the old article title. You can then choose to leave the redirect in place or delete the old title later.
It can be useful to put redirect pages under common alternate terms for the same topic. But don't get carried away.
An alternative to a redirect is a disambiguation page, which links to several possible articles under the same title.