Cross-selling vs. upselling
Cross-selling gets customers to buy additional or related products to their original purchase, to increase business revenue and the average order value per user. Upselling convinces a customer to upgrade their original choice at a higher cost.
Say you switch to a Pro version of a smartphone after a recommendation from the vendor. That's an up-sell. If you buy a leather case for your phone at checkout, that would be considered a cross-sell.
With a customer engagement solution like Twilio Engage, you can better identify these opportunities for cross-selling or upselling depending on the user's behavioral and purchase history (among other traits).