Java EE applications are made up of components. A Java EE component is a self-contained functional software unit that is assembled into a Java EE application with its related classes and files and that communicates with other components.
The Java EE specification defines the following Java EE components:
Application clients and applets are components that run on the client.
Java Servlet, JavaServer Faces, and JavaServer PagesTM (JSPTM) technology components are web components that run on the server.
Enterprise JavaBeansTM (EJBTM) components (enterprise beans) are business components that run on the server.
Java EE components are written in the Java programming language and are compiled in the same way as any program in the language. The difference between Java EE components and “standard” Java classes is that Java EE components are assembled into a Java EE application, are verified to be well formed and in compliance with the Java EE specification, and are deployed to production, where they are run and managed by the Java EE server.