In most cases, the term "app" is used to refer to a mobile application. This type of software is often much smaller and more specific than that on a PC. So, while a slick software suite provides full functionality, an app usually has an arrow and specific function-or very little function at all, as many mobile applications are designed for entertainment. This type of application was popularized by Apple through its App Store, where applications are sold for a few dollars a piece.These apps work only on Apple devices. So, other companies have followed Apple’s lead, creating apps for Android and Black Berry devices.