A web app is a software application that runs on a web server and can be accessed through a web browser. Unlike traditional desktop applications, web apps do not need to be installed on a user's device. They are designed to be interactive and can perform various functions, such as managing data or facilitating communication. Web apps are built using standard web technologies like HTML, CSS, and JavaScript. They can be used on different devices, including computers, tablets, and smartphones, making them versatile and accessible. Popular examples of web apps include Google Docs and Facebook.