Q.What is the difference between an item's main image and sub images?

An item can have up to 20 images, including one main image and up to 19 sub images. These are all uploaded in the same place, in the Images field of the Shop Manager item description page. The main image is the leftmost image displayed on this page,

Main image will be displayed on item list pages:

They will also be displayed as the large image by default on the item description page.

Sub images will only be displayed full size when selected by the customer: