Primary Web Item
Having a primary web item will allow you to choose which image will appear on your lists of Artists as your first piece on your website. If the item that is being used as the primary web item (also known as the "first title" in Masterpiece version 9) is sold or put on approval, then the website can randomly display a different item automatically. It all depends on how you prefer this feature to work.
To select the primary web item, just search for the artist you are adding a primary web item to and double click to edit
A screen will appear with all the inventory that is listed by that artist. You can only select one item as a primary.