Click "+" on the tree to the left to open a folder. Click "-" to close a folder.
Click on a folder (or the text next to it) and see what happens. Click "About this demo" to learn more.
Clicking on "About this directory" either here or in the Surftree™ to the left is a good place to learn more. If you would like to use a tree like this on your website, the tree is available from Dataroo.