A web application, commonly referred to as a web app, is a software application that runs on a web server rather than being installed on the local computer. It is accessed through a web browser and requires an active internet connection to function. Web applications utilize web technologies such as HTML, CSS, JavaScript, and server-side languages (like PHP, Python, Ruby, etc.) to provide users with interactive experiences.

Key characteristics of web applications include:

1. Access via Web Browser: Users access web applications through a web browser like Chrome, Firefox, Safari, etc.

2. Internet Connectivity: Web applications require an internet connection to function as they rely on resources hosted on remote servers.

3. Cross-Platform Compatibility: Since web apps run in a browser, they can be accessed across different operating systems (Windows, macOS, Linux, etc.) without requiring platform-specific versions.

4. Client-Server Architecture: Web applications typically follow a client-server architecture where the client (user’s browser) interacts with the server (where the application logic and data are stored).

5. Dynamic Content: Web applications can dynamically generate content based on user interactions or data retrieved from databases or other sources.

Examples of web applications include social media sites like Facebook, e-commerce platforms like Amazon, online banking systems, web-based email clients like Gmail, and productivity tools like Google Docs.

Overall, web applications have become integral to daily internet usage due to their accessibility, versatility, and ability to provide interactive and collaborative experiences over the web.