So when you create new domain you do not need to go to server console and create resources such as data source, etc. While creating domain by using template you will have those resources configured already for you.
Lets say, you have a team and you like everybody to have same configuration, then create a template share with the team. Even it is very much useful if you have new member in the team.
1]. Go to $WL_HOME/common/bin & run config_builder.cmd ( Win ) , config_builder.sh ( Unix/Linux )
2]. Click on "Create a Domain Template"
Select template name & location and click on next
Select "Select a template" , select "Basic Weblogic Server Domain" option and next
Select default and next
Enter username and password for your domain
Add the resources from your existing domain to the new domain you are going to create, next
Select your database, next
Enter you Admin Server name , listen address and port, next
Click on Create Domain
Now, Run the domain creation wizard and during prompt select domain source, select your above created template.