It looks like you're using Firefox/Firebug. You can check the Firebug wiki for a definition of the different request phases. (Other browsers have similar names.)
In your case, Waiting reflects the time between request and response, as Brad mentioned. That row you highlighted shows a wait of 12.66s for the server to start responding, then just 6ms spent receiving the data.
To resolve that you'll need to debug within your application itself. Tools like YSlow and PageSpeed are good for the front-end components (JS, CSS, images, etc.) but won't help you diagnose the initial page load speed directly.