The IBM WebSphere Application Server product uses the following definitions:
Deployment Manager The deployment manager is the central administrative manager. It does not install the base WebSphere Application Server product on other machines. Only one system hosts the deployment manager.
Cell A cell is made up of nodes (servers) containing node agents, which are managed by a deployment manager. As the deployment manager federates base WebSphere Application Server nodes, it expands the cell that it manages.
Clusters A cluster is a group of servers that can be used together for workload balancing by creating additional, nearly identical copies of an application server configuration. This group is the equivalent of BEA's cluster. Clusters are identical multiple Application Server copies. See the IBM WebSphere Application Server documentation for more information: http://www-306.ibm.com/software/webservers/appserv/was/library/library51.html
WebSphere Application Server Network Deployment edition addresses application servers that run in multiple-server production scenarios. It provides centralized administration, as well as basic clustering and caching support.
WebSphere Advanced Server Network Deployment provides a more robust approach to clustering because it includes a database. In Advanced Server, all servers use the database for the configuration information. You can use the WebSphere administration console, a Swing Java application, or the command-line utilities XMLConfig and wscpthen to manage the servers.