A desktop application is a software program that is installed locally on a user's computer and runs on the computer's operating system. A web application, on the other hand, runs on a remote server and is accessed through a web browser over the internet.

Desktop applications have the advantage of being able to run offline, having access to a user's local resources such as files and hardware, and providing a more responsive user experience since they don't have to communicate with a remote server for every action.

To ensure the security of a desktop application, one should follow best practices for software development, such as implementing proper authentication and authorization mechanisms, input validation, and secure data storage. It's also important to regularly update the application and its dependencies to fix any known security vulnerabilities.