What is an App?
Internet Marketing Dictionary | ipod Apps and other Apps explained

An App is a simple program that performs a specific function often on a small computer like Apple's iPod or iPhone.

Apps really took off when Apple introduced the iPhone and started to sell and distribute them via its iTunes service. Software developers could think of a specific thing they wanted the iPhone to do such as play Sudoku, or Chess, or act as a gaming device or a mapping tool and then use a development tool provided by Apple to design and build the program. Once approved by Apple an App could be downloaded onto iPhones quickly and easily over the internet.

To begin with many Apps were free and then businesses started to develop paid for Apps. In many cases free versions of Apps were offered that provided a limited set of functions in order to encourage users to upgrade to the paid version.

Apps are now regarded as small software applications that perform a relative limited range of functions. However as the computing power of small devices increases so too does the range and capabilities of apps.

The business of developing and selling Apps has also grown dramatically and well over 2,000,000,000 Apps have now been downloaded via iTunes which is an absolutely vast number. Furthermore there are well over 100,000 different apps available. Many of these cost just a few dollars and provide valuable additional functionality for iPhone and iPod users.