1) Business model 
Cross-selling is the action or practice of selling an additional product or service to an existing customer. This article deals exclusively with the latter meaning. In practice, businesses define cross-selling in many different ways. Elements that might influence the definition might include the size of the business, the industry sector it operate...
The sale of a product to customers who already purchase a different product from the supplier....more on Cross selling
Using a customer's buying history to select them for related offers, e.g. a car alarm for new car buyers.