Prefixes allow you to select predefined text that appears before a Modifier. It is used to easily notify the kitchen regarding specifications to the menu item that has many ingredients.
The Prefixes available for a Modifier appear on the right-side of the Order screen:

Select any one of the Prefixes, and after selection it will be appear under the item in red text:

Note: If the prefix contains No, then the respective Modifier will not be added to the Menu Item. If the Modifier has been added as an Included Modifier from Back Office, then the Price defined for the Prefix will be applied.