Apache Wicket is an open-source web application framework for building complex and scalable Java web applications. It focuses on building component-based web apps that can be easily maintainable, reusable, and testable. It provides a high level of abstraction, making it easier for developers to implement business logic separately from the UI. Wicket is built on top of JavaServer Pages (JSP) and Java Servlets, and it uses the Model-View-Controller (MVC) design pattern. It is widely used in enterprise applications for its simplicity, modularity, and robustness.