Java Servlets are server-side programs that handle requests and responses in web applications. They are written in the Java programming language and run on a web server, allowing developers to create dynamic web content. When a user sends a request to a server, the servlet processes the request, interacts with databases or other resources, and generates a response, typically in the form of HTML. Servlets are part of the Java EE (Enterprise Edition) platform and are commonly used in conjunction with JavaServer Pages (JSP) to create robust web applications. They provide a way to manage session data and maintain state across multiple requests, enhancing the user experience on websites.