Modifiers are special categories with with products in them that can be either add to, removed from, or required for other products that are made up of different elements.
Examples of this would be removing lettuce from a hamburger, adding extra creme to drink, or how you want your steak cooked.
The following are short descriptions of the three different types of modifiers.
Modifier + category is used to add additional options for an item. (Example: Adding a sauce to a sandwich)
Modifier - category is used to remove items that would normally come with an item. (Example: Removing onions from a pizza)
Forced Modifier category is use for options for an item that are required. (Example: What side item the customer wants with their meal)