This file is to make it easier to get up and running in a PenTest or vulnerability assessment with Nessus and metasploit. 

To make it simple this file is called by you at the command line when you start msfconsole or any metasploit command when 
you will need the database connection. 

For msfconsole the command would be msfconsole -r Template.rc

The way I use the file it to make a copy of the file and name it the name of the client. Then I edit the file and have the database
portion point to the client name. That will get the system setup to start the assessment.