What is a WebSphere Application Server Mean by a Server?

Any server in WebSphere Application Server is a collection of services and components that execute in the context of a java virtual machine. WebSphere Application Server, the product, is capable of creating many different kinds of servers.

• Application servers host J2EE enterprise applications. Most people think of this kind of server when they use the word "server". Your J2EE applications execute inside the various containers of the ApplicationServer component of this server.
• Web servers. This term is a little misleading. It is not a real server like the IBM Http Server or like the Apache web server. Rather, it is a thin piece of code that controls any of the web servers that IBM supports.
• Proxy servers
• Generic servers are any J2EE server not supplied by WebSphere. Examples would include JBoss and Resin
• Node agents control nodes. Specifically, node agents make configuration changes ordered by a deployment manager and they report the status of the servers in their node back to the deployment manager. Node agents are also able to start and stop servers in their node.
• Deployment managers control cells. They hold the master configuration records for every server and every application and every bus in the cell.

Each kind of server has its own mixture of components and services. Node agents, for instance, do not have an application server component. Some servers -- notably web servers and generic servers -- are really not servers at all. They are just thin facades that control the real servers.