That milestone setting download was not named, but Apple did say that nearly 20 billion of the downloads took place in 2012. Apple is now selling apps in 155 countries around the world with 775,000 apps in stock, more than 300,000 of which were developed natively for the iPad. iTunes saw a had a record-breaking two million app downloads in December and reportedly has more than 500 million active accounts.
Apple has been making apps for nearly as long as they have been developing the OS running on their hardware, but in this case the term app store refers to the 3rd part app store which Apple launched in 2008 to support the locked down iOS platform. Apple has since expanded the app store to offer apps for OSX, including both Apple's own word as well as 3rd-party apps.