Firstly, I want to say that, I just started learning NSO, that is why my question might be primitive, sorry for that.
What are the template files (XML files under template folder) ?  why they are used? when they should be changed?  and mainly, who uses those templates after applying parameters to templates?  Let's say I apply new parameter to template, should I change template accordingly?   
Would be much helpful if you help me to understand this part