11.What is a Cluster in Oracle Weblogic server?
A cluster is a Logical group of Weblogic servers. Oracle Weblogic server provides HIGH AVAILABILITY & LOAD BALANCING with help of cluster.
12.What is a Node Manager?
A Node Manager is a utility or process running on a physical server that enables starting, stopping, suspending or restarting the Administration and Managed servers remotely. It is not associated with a Domain. [Node manager can start any server instances that are resides on the same physical server].
13.How many ways we can install Oracle Weblogic Server?
You can install Oracle Weblogic server in three different ways.

GUI mode (extract server103_linux32.bin/double click on server103_win32.exe )
Console mode (c:\>server103_linux32.bin –mode=console –log=c:\consoleinstal.log)
Silent mode (c:\> server103_linux32.bin –mode=silent –silent_xml=path_to_silent.xml –log=c:\silentinstal.log)

14.What is the default database for Weblogic server?
Point base is the default database. This database comes along with Weblogic software bundle.
15.How many ways we can configure a domain?
You can configure Oracle Weblogic server domains in two ways.

Graphical Mode (config.cmd [Scripts are in the <WL_HOME>/common/bin directory])
Console Mode (config.cmd –mode=console)

16.How many ways you can start Administration server?
You can start the Administration server using 5 ways.

weblogic.Server (only in development)
Start menu (only Windows)
DOMAIN_DIR/bin/startWebLogic.sh
WebLogic Scripting Tool (WLST) and Node Manager
WLST without Node Manager

17.How many ways you can configure managed servers?
You can configure the Managed server using 3 was.

Domain Configuration Wizard
Administration Console
Command Line (WLST)

18.How many ways you can configure a machines?
You can configure machines by using following:

Domain Configuration Wizard
Administration Console
Command Line (WLST)

19.How many ways you can start managed servers?
Start Managed Servers by using:

weblogic.Server
DOMAIN_DIR/bin/startManagedWebLogic.sh
Administration Console
WLST and Node Manager

20.How do I provide user credentials for starting a server?
When you create a domain, the Configuration Wizard prompts you to provide the username and password for an initial administrative user. If you create the domain in development mode, the wizard saves the username and encrypted password in a boot identity file. A WebLogic Server instance can refer to a boot identity file during its startup process. If a server instance does not find such a file, it prompts you to enter credentials.

If you create a domain in production mode, or if you want to change user credentials in an existing boot identity file, you can create a new boot identity file. WebLogic Server does not support copying a boot identity file from one server root directory to another. For information on creating and using boot identity files, see Boot Identity Files in Administration Console Online Help.