A Java Servlet Container is a component of a web server that manages Java Servlets, which are Java programs that run on the server side. It provides the environment for servlets to execute, handling requests from clients, processing them, and returning responses. This allows for dynamic web content generation, making it essential for Java-based web applications. The servlet container also manages the lifecycle of servlets, including their creation, initialization, and destruction. Popular servlet containers include Apache Tomcat and Jetty, which implement the Java Servlet API, ensuring compatibility and standardization across different web applications.