An Application Server is a software framework that provides the environment for running web applications. It acts as a mediator between the user interface and the backend database, handling business logic and processing requests. This allows developers to create dynamic web applications that can respond to user inputs in real-time. Typically, an application server supports various programming languages and frameworks, enabling developers to build applications more efficiently. It often includes features like security, transaction management, and scalability, making it essential for enterprise-level applications. Examples of popular application servers include Apache Tomcat, JBoss, and Microsoft IIS.