A Java EE application is packaged into one or more standard units for deployment to any Java EE platform-compliant system. Each unit contains:
A functional component or components (such as an enterprise bean, JSP page, servlet, or applet)
An optional deployment descriptor that describes its content
Once a Java EE unit has been produced, it is ready to be deployed. Deployment typically involves using a platform’s deployment tool to specify location-specific information, such as a list of local users that can access it and the name of the local database. Once deployed on a local platform, the application is ready to run.