In Short

BlackBerry World is the on-device storefront through which users can download apps and games. Previously, the portal was known as BlackBerry App World, but was renamed after the separate marketplaces created on the PlayBook were folded together for BlackBerry 10. 

BlackBerry World allows users to pay for their content through credit card, PayPal, or directly through their wireless service provider (when supported). Apps can be downloaded directly from the device by conducting searches or browsing through the categorized catalog. A web portal to the store also allows users to remotely install content onto their device. Though the BlackBerry World is a unified marketplace, selection varies between BlackBerry OS 7 devices, BlackBerry 10 devices, and BlackBerry PlayBook.