Configuring Billing Services Feature
Enable Billing Services feature from Essential Kit Settings
Billing product is a container to hold your in-app purchase identifiers for different platforms. Each billing product has a unique Id to identify them. Id helps in referring an in-app purchase from your code irrespective of the platform you are on and this can be any string of your choice.
Platform Id on the other hand, is the actual platform specific identifier and usually varies per platform. Specify the value in platform overrides, if you don't have a common identifier among platforms.
You can have your purchasable items both Consumable and Non-Consumable.