The cart as a page, navbar to footer: editable lines beside the order summary, then products picked for the order, so a shopper keeps browsing on the way to checkout. Two finished pages.
A section is one full-width band: a hero, a pricing table, a footer. A page stacks several of them into a finished screen, from the navbar to the footer. The sections are the parts, the page is one tested way to put them together.
Koala UI