From the site:
If you are a visual person, a simple list of your tasks may be hard to follow. With a concept like Task Boxes, you can prioritize your tasks. The idea is simple: The most important task goes in the biggest box. Other tasks go in the other boxes, in order of importance.
Creating a Task Box is as simple as drawing a few lines on a note card or Post-It note. Use them to make lists daily, weekly, monthly.