Elements on a page are like objects in the real world. They share space and push each other around.
Click and hold an element to start dragging it on a page. The label found above the dashed purple lines display the immediate box the element is being dragged within.
Thick purple lines show where the element will be placed. Elements can be placed above and below, or side-by-side with other elements.
Boxes can also be sorted using an elements breadcrumbs.