First of all, a URL is a Uniform Resource Locator, and it points to a particular machine's IP (interneet protocol) address, which it finds on a DNS (domain name server). A URL Redirect is a system of having multiple URLs to point to the same IP address, so that a particular website may be accessed in more than one way (with more than one URL).
MechanicsThis isn't about physics. It's about the Internet. URL Redirects work in this way: the company that provides the redirect registers the new URL that you want to point to your site, then creates a "dummy" page that links to your real content. They use frames, which is annoying to some end users (like yourself, who are browsing the Internet) and to most webmasters. The technical setup includes a simple HTML (HyperTextMarkupLanguage) page with two frames, one of size zero, and the other that fills the viewport (the part of the window that the page is in) entirely and loads your home page.
ProblemsOne major issue with this is that the end user, who is, of course, very experienced, does not get to see the full path to the file that they are actually viewing; it is hidden in the frame source. If this experienced end user were to save the source code for the page without reading it, he would inevitably get the frame container page from the redirect folks. Instead, using an advanced browser like Mozilla's Firefox, he would have to save the Frame from the context menu (when you right-click). Such hassles can be defeated with a little cash - register your own domain name!