A tag cloud is a name for a collection of keywords that are displayed as a big block of text. Usually the most commonly occurring keyword is the largest, and the least commonly occurring keyword is the smallest. Tag clouds are a neat way of allowing your users to navigate your content in a different way, simply be letting them look over the cloud and linking each keyword to sections of your site that contain that word.
Wordpress comes with this function built in and is already available as a widget. However, after adding a few hundred posts this tag cloud can get rather large and this widget can stretch your sidebar to stupid proportions. A way around this is to create a page that can be used to display this large tag cloud. The first step is to create a page template that will be used to run the correct Wordpress function to display the tags. This is done by making a copy of your normal page template (call it tagpage.php) and adding the following code at the top.