Cross-selling is a list of items you want to suggest for selling or questions you need answered when certain items are sold.
Infocodes are used for cross-selling.
If there is more than one list of items that you want to display (that is, you created more than one cross-selling infocode), you can group these cross-selling infocodes together with a cross-selling group infocode. Then you only need to link the cross-selling group infocode to items (or product groups or item categories).
See also
How to: Create cross-selling Groups
How to: Assign Cross-selling to an Item, Product Group, or Item Category
How to: See What Cross-sellings Are Assigned to an Item