Domain : It is logical related group of Oracle Weblogic server resources that are managed as a single unit.
Server : We can define a server in number of ways , say a server is a computer or laptop in the concept of what a hardware server is. But in weblogic , if we use the term Server, it means an instance of a weblogic server. So Weblogic server is a process that runs on a designated machine. There are two types of servers available to us, namely administration server and managed servers in weblogic.
Administration Server : Administration Server is the central point for a domain. It stores all the configuration information and log for a domain. It is the server which is incharge of the domain. From an administrative stand point, whenever we want to do any monitoring or management of anything in a domain, we do that through communicating with the administration server. Every domain must have one and only one administration server.
Managed Server : A managed server is the server which hosts applications. These are the servers in a domain which does the actual work. We can have multiple managed servers within a domain.
Machine : A machine is a computer that hosts the weblogic server instances. It is used by the node manager to start the failed managed server.
Node Manager : A node manager is a separate utility which runs on machines which are hosting weblogic. We can use node manager to remotely startup weblogic servers.
Cluster : A cluster in a weblogic server is defined as a logical group of weblogic servers. It provides high availability and scalability. A cluster is defined within a single domain and it cant span domains. So all the servers in a cluster should also be in same domain. Only managed servers can make up a cluster.
J2EE technologies : Here I want to list the J2EE technologies used in weblogic server. They are Java Servlets,JSPs,EJBs, JDBCs,JNDIs,JTAs, JMSs, JAAS and JMX.