This introduction provides the reader with details on a few different topics - making a custom template for the user login form, pass an "editable node" into said form, alter the values in it, and make the page easily accessible for the template file.

Being a tutorial, he steps you through every bit of the way, complete with code and explainations (and screenshots) to make the lesson easier. You'll need to know some PHP before getting into this - it's more than just a simple HTML template change.