what is the work of node manager and how do you configure it ?

ANSWER:
Node manager is especially used for remote managed server startup.
We require a logical machine created from Weblogic Admin console.

Domain ---> Machines --> NewMachine --> Nodemanager(we need to provide the host and the port on which nodemanager is running , by default it will be localhost and 5556)
Start the nodemanager from Bea-home/weblogic-home/common/bin/startNodemanager.sh (E:/bea92/weblogic92/common/bin/startNodemanager.cmd)