Upselling is a sales technique where a seller encourages a customer to purchase a more expensive item, an upgrade, or additional features to enhance their original choice. This strategy aims to increase the overall value of the sale while providing the customer with a better experience or product. For example, when buying a smartphone, a salesperson might suggest a model with more storage or a protective case. By highlighting the benefits of these options, the seller helps the customer make a more informed decision while boosting the store's revenue.