Infants learn from active experience 

Repeated perception-action cycles with embedded exploration and selection provides the experience needed for learning new abilities. 

Let's start at the beginning 1

Infants s are born with a set of abilities that provide the first experiences which in turn create the basis for new learning. 
So a good place to start understanding typical and atypical development is start at the beginning and review early infant behaviour. 

Lets start at the beginning 2   Newborn movement abilities 

Newborn spontaneous movement kickstarts motor development 

Infant behavior is always complex 

Any action emerges from the complex interaction between different  body-brain systems (arousal, motivation, postural, movement, attention, auditory, visual, emotion, social) and the physical and social environment. 

All new learning builds on present abilities 

The cascade principles and starting with infant strengths

Learning occurs when the infant actively engages with a task 
Learning requires exploration of different ways to achieve an outcome - and this requires intention and goals. 

Success is important for motivation 
Infants are very sensitive to successful outcome of an intentional action: and success has the added benefit of providing a spurt of dopamine which enhances learning and motivation to try again.. 

Early spontaneous movement changes to curiosity driven actions and then intentional, goal oriented action

How the factors that drive development and learning change over time