Tattling is an important process to teach a child what is proper, unacceptable or tolerable behavior in their family and on a larger scale, what is acceptable or expected in the community or nation.  A young child runs to tell on an older sibling, not understanding the older child perhaps has more privledges because of maturity or because the older child has different responsibilites.  The young child learns that some observed actions are unimportant while others get the sibling punished.  

Tattling helps a child figure out what is important behavior, what is dangerous and what will lead to punishment.  It is a necessary process for child development.

A child who constantly tattles, in order to get another person in trouble, is labeled a "tattletale."   Family members can and will target a tattletale in order to get even with the irritating little person. 

On the other hand, a child who is silenced from "tattling" for any reason, or is told to "shut up" teaches the child their voice is unimportant.   They learn to keep silent, never asking questions.