Temperament
The way a child is wired from birth, and why two children can meet the same moment in completely different ways.
Articles
Three factors shape every child: temperament, development, and environment. The articles here are sorted by those three. Start with whichever one sounds most like the child you are thinking of.
Development
Most children have no issues with development. One child in six will have what is called a neurodevelopmental disorder.
Environment
The nurture side: the world a child grows up in, and what parents and communities can change.