Joomla! since version 2.5 has this cool little features of where you can create a vanity URL or redirect a broken URL in a website to a proper working one.
The component that allows this is called Redirect.
It captures all of the broken links, of 404 errors that appear in the website and allows a website administrator to redirect them to the right or correct pages in a site.
Take this example, joomlabe.at/mailmaner has a little typo in the address, but I've just sent it out to my entire email database list. Since it is in everyone's inbox now, there is nothing I can do in regards to changing the link in the mail out. Instead I can redirect that broken link on the website to the proper page, joomlabe.at/mailmanager, a save the email blast that I just did.