This panel allows you to re-order the panels on your checkout. It is found in the WSM under Design & Content -> Checkout.
How To Use
The panels in the list Ordered Panels are represented by drag-able boxes. To move a panel, click on it and drag it to its new position. When you are happy that the order is correct click the green Save button.
Ordered Panels vs Unordered Panels
On the left is a list of panels that haven't been ordered. Unordered panels will still appear on the checkout according to an arcane and mysterious formula. If you want to force an unordered panel into a particular position, drag it from the Unordered Panels list to the Ordered Panels list on the right.
This interface won't switch off panels, you need to use the correct option associated with that panel to switch off a panel.
Because of its importance to the checkout, the Customer Panel cannot be moved from the first position. You won't be able to drag any panel to be above it.