The price group descriptions allow you to set a custom description for a product per price group (if desired). If no custom description is set, then just the default standard item description is used. The descriptions can be set manually in the catalog item or done in bulk with the item template csv file.
Go to Business -> Settings, and turn on the Pricing Descriptions feature:
Once this feature is turned on, you will then find the ability to set pricing descriptions on a catalog item, when you try to edit the catalog item in the catalog:
You can also set this if you download the ‘Item Template CSV’ file to make bulk edits to the catalog.