There are three types of product relations in Magento: Up-sells, Related Products, and Cross-sell Products. When viewing a product, Upsells for this product are items that your customers would ideally buy instead of the product they’re viewing. They might be better quality, produce a higher profit margin, be more popular, etc. These appear on the product info page. Related products appear in the product info page as well, in the right column. Related products are meant to be purchased in addition to the item the customer is viewing. Finally, Cross-sell items appear in the shopping cart. When a customer navigates to the shopping cart (this can happen automatically after adding a product, or not), the cross-sells block displays a selection of items marked as cross-sells to the items already in the cart. They’re a bit like impulse buys – like magazines and candy at the cash registers in grocery stores.
This is the example of the Up-sell. Ideally, the visitor is supposed to analyze those products as they should be relevant to the one that is just loaded.