The Application Server creates one application server instance, called server at the time of installation. You can delete the server instance and create a new instance with a different name.
For many users, one application server instance meets their needs. However, depending upon your environment, you might want to create additional application server instances. For example, in a development environment you can use different application server instances to test different Application Server configurations, or to compare and test different application deployments. Because you can easily add or delete an application server instance, you can use them to create temporary “sandbox” areas to experiment with while developing.