If you mean exactly those products that will be displayed on the site, then there is a series of settings.
1. Display or not display products out of stock
2. In the settings of each category of goods there is a corresponding. checkbox "Do not display on the site"
http://i.imgur.com/xOKRMRi.png3. There is a setting - do not display empty categories
4. Separate settings for banners and lists
etc.
Thus, there is no way to describe showcase editing in one sentence