Redirects are used to forward users from one page name to another. They can be useful if a particular article is referred to by multiple names, or has alternative punctuation, capitalization or spellings.
Creating a redirect
To create a redirect, you must start a new page with the name you want to direct from and enter the following text:
where pagename is the name of the page you want to redirect users to.
You can use the 'preview' button, to check that you have entered the correct page name (Generally you will be redirecting to an existing page name, so the link should be blue, not red)
Viewing a redirect
After creating a redirect, you can no longer get to that page name. The browser is always redirected! However near the top of the page, a link is provided. Click this to get back to the redirected page name, and "view" the redirect.
By doing this, you can do all the things that any wiki page allows. You can go to the associated discussion page to discuss the redirect. You can view the history of the page before the redirect was put in place. You edit the page if the redirect is wrong, and you can revert to an older version to remove the redirect.
Deleting a redirect
There's generally no need to delete redirects. They do not occupy a significant amount of database space, and they do not show up in wiki search results. If a page name is vaguely meaningful there's no harm (and some benefit) in having it as a redirect to the most relevant existing page in your wiki. However...
If you do need to delete a redirect, e.g. if the page name of the redirect is offensive, or you wish to discourage people from referring to concept by that name, then you simply go to the redirect page, and follow the same procedure for deleting a page. See: Help:Deleting a page
A double redirect (a page redirecting to a page which is itself a redirect) will not work. The redirecting will not follow through to the end of the chain. Instead people will just be presented with the relevant link (a view of the redirect page). This is a deliberate restriction, partly to prevent infinite loops, and partly to keep things simple. It avoids people building up an unpleasantly complicated tree of redirects!
However this does mean that you should look out for double redirects and eliminate them, by changing them to be 1-step redirects instead. You are most likely to need to do this after a significant page move. Use the 'what links here' toolbox link to find double redirects to a particular page, or use Special:DoubleRedirects to find them throughout the whole wiki.