Developmental milestones provides a way to track the growth of children.
It provides information around various things a child should be doing at any particular age since the birth.
Not every child is the same. Hence not every child will be displaying all these attributes exactly as written but majority of these are true for majority of the children.
These milestones effectively help in 2 aspects
Tracking the growth of the child.
Identifying the areas where parents should act on, incase there is any difference between the growth of the child versus the milestones.
Resources for develomental milestones
You can get in-depth details about the developmental milestones from the following sources.