What is an application? You may have heard people talking about using a program, an application, or app. But what exactly does that mean? Simply put, an app is a type of software that allows you to perform specific tasks. Applications for desktop or laptop computers are somethings called desktop applications, which those for mobile devices are called mobile apps. When you open an application, it runs inside the operating system until you close it. Most of the time, you will have more than one application open at the same time, which is known as multi-tasking. App is common term for an application, especially for simple applications that can be downloaded inexpensively or even for free. Many apps are also available for mobile devices and even some TVs. Desktop applications There are countless desktop applications, and they fall into several categories. Some are more full featured (like Microsoft Word ), while others may only do one or two things (like a clock or calendar app).