Forms for the foundation walls are set in place on top of the footings.  The forms help to shape the foundation walls and are coated with a special oil that helps them to be removed. Concrete will then be poured into the forms.  Once the concrete has had time to set, the panels will be removed, leaving foundation walls.

What is difficult to imagine is that, at this point, what you are looking at will actually be underground.  This will become more evident as the building begins to take shape.