Magento – Difference between up sell products and cross-sell products

Up sell products are items that customers would preferably buy instead of the product they’re viewing. This may be an expensive model, better quality and/or more popular of the same type of product.

I.e. the customer is looking for a 8GB iPod Nano for $129.00. The up sell products can be the following:
– 16 GB iPod Nano $149.00
– 8 GB iPod Touch $199.00
– 160GB iPod Classic $249.00

Cross sell products are items that are related to the purchased (or intended to buy) items. Usually these are accessories compatible with your purchased product that are sold separately. It may also include added features/warranties.
Some of the cross-sell products from the given sample above:
– Bose® QuietComfort® 15 Acoustic Noise Cancelling® Headphones (with Remote and Mic)
– JAMBOX by Jawbone Wireless Speaker – Black
– Apple USB Power Adapter

Common labels for recommendations (both upsell and crossells) are:
“What do customers buy after viewing this item?”
“More customer favorites”
“Recommended products”
“You may also like”
“Customers who bought X also bought”
“Customers who viewed X also viewed”
“Frequently bought together”
“Stuff you need” (Radio Shack, for accessories)
“Stuff you may want” (Radio Shack, for items in other categories)
“More from this (category, brand, author, artist)”