Applications can be included in a computer's operating system or sold separately, and they can be written in proprietary, open-source, or project code.

Apps for mobile devices, such asphones, are frequently referred to as 'apps.'

An application, application program, or application software in information technology is a computer program that assists people in doing a task. An application can manipulate text, numbers, audio, pictures, and a combination of these elements depending on the activity for which it was created. Some application packages specialize in a single task, such as word processing, while others, known as integrated software, include multiple programs.

The meaning of the adjective 'application' is not limited to 'of or pertaining to application software.'

User-written software customizes systems to match the demands of the user. User-written software includes spreadsheet templates, word processor macros, scientific simulations, music, graphics, and animation scripts, among other things. Email filters, too, are a type of user software. Users design this software on their own and frequently underestimate its importance.

Not only do terms like application programming interface (API), application server, application virtualization, application lifecycle management, and portable application apply to application software, but they also apply to all computer programs

In terms of the rights of its final end-users or subscribers, application software is typically classed using a black-box approach.

Software applications are also classified according to the programming language in which the source code is created or run, as well as the goal and outputs of the software.

The abbreviated name 'app' has become widely used to refer to applications for mobile devices such as smartphones and tablets, with the reduced form reflecting their often lesser scope as compared to PC software. Recently, the shorter version has also been utilized for desktop application software.