What type of application must be installed on a computer operating system?

A desktop application is a type of software that is designed to be installed and run on a personal computer or laptop, utilizing the operating system's resources directly. Unlike web applications, which run in web browsers and rely on an internet connection, desktop applications are installed locally, allowing them to operate more independently of web infrastructure.

This independence grants desktop applications access to the local file system, hardware, and operating system features that web applications may not fully utilize due to security and access restrictions inherent in web environments.

Mobile applications are specifically built for mobile devices, and while they do require installation, they run in a different environment than a traditional desktop operating system. Remote applications often refer to software that is accessed through the cloud or a remote server but may still require installations on remote devices. Therefore, the defining characteristic of a desktop application, being installed directly on a computer's operating system, aligns it closely with the question asked.