A web application is an application delivered to users from a web server and is accessed using a web browser. Some companies may run a web application on their intranet as well.
A desktop application is an application that runs standalone on a desktop computer or a laptop and can perform a set of tasks under the user control.
And now the pros and cons to each of them:
Installation and updating: Web applications are installed once where as desktop applications need to be installed separately on each computer / laptop. Updating the desktop applications needs to be done on every single computer which is not the case with web applications.
Security: In terms of security, web applications are exposed to more security risks than desktop applications. While you have almost total control over the computer that runs the standalone applications, it’s not the case with web applications, which are more exposed to internet threats.
Speed and connectivity: Web apps rely very much on the internet connectivity and speed. If there’s no internet or poor connectivity, the web apps will encounter performance issues or will not work at all. Desktop apps, being standalone by nature, won’t face any issues resulting from internet connectivity.
Cost: Web apps are usually more expensive over time. Desktop apps are purchased once and rarely have maintenance fees or fee based upgrades associated with them. Web applications use a different model, users typically are charged a monthly service fee, or a subscription fee to operate the software. If you don’t renew your subscription you might not be unable to use the data the web application stored.
These are only the basics of desktop apps and web apps. The selection of a suitable app will entirely depend on the business needs and factors, based on the comparison above.