A web application or "web app" is a software program that runs on a web server. Unlike traditional desktop applications, which are launched by your operating system, web apps must be accessed through a web browser.
Web apps have several advantages over desktop applications. Since they run inside web browsers, developers do not need to develop web apps for multiple platforms. For example, a single application that runs in Chrome will work on both Windows and OS X. Developers do not need to distribute software updates to users when the web app is updated. By updating the application on the server, all users have access to the updated version.
From a user standpoint, a web app may provide a more consistent user interface across multiple platforms because the appearance is dependent on the browser rather than the operating system. Additionally, the data you enter into a web app is processed and saved remotely. This allows you to access the same data from multiple devices, rather than transferring files between computer systems.
While web applications offer several benefits, they do have some disadvantages compared to desktop applications. Since they do not run directly from the operating system, they have limited access to system resources, such as the CPU, memory, and the file system. Therefore, high-end programs, such as video production and other media apps generally perform better as desktop applications. Web apps are also entirely dependent on the web browser. If your browser crashes, for example, you may lose your unsaved progress. Also, browser updates may cause incompatibilities with web apps, creating unexpected issues.
Some people prefer desktop apps, while others prefer web applications. Therefore, many software companies now offer both desktop and web versions of their most popular programs. Common examples include Microsoft Office, Apple iWork, and Intuit TurboTax. In most cases, files saved in the online version are compatible with the desktop version and vice versa. For example, if you save a .TAX2013 file in TurboTax Online, you can open and edit the file with the desktop version.