What is the difference between a background image and a logo?

A background image: Has text and/or photo frames, and other graphics can appear on top of it. Background images are applied to the full bleed size of the document you are creating (but you can reduce its size after uploading).

A logo: Appears on top of other design elements (for example, your uploaded background image or a design that is part of the template). However, it is possible add text on top of a logo image.