Predefinition allows to display filter that adapts to the current request by default. For example if you want to show in the filter only  for "on sale" products.  OR only  for "Summer" products

Examples:  On sale    AND   Summer

Predefinition allows to generate relevant filter for shop articles about special defined products.

How to fill in each field is indicated in the information:

Everything seems simple. But including/excluding by taxonomy can be difficult:

For this field, you should know two values: taxonomy slug and term ID - go to the page for editing terms and point the mouse at the inscription "edit":