Start with this article on the Keys to Brain Development. In order to learn, children need to have a balance of novelty (new experiences), the chance to explore things again and again to gain mastery (repetition) and some down time to process it al.
Other helpful overview articles are: Developmental Milestones, Understanding Your Child’s Temperament; Gender Differences: Nature then Nurture; Emotional Literacy Overview; Building Social Skills; and Building Fine Motor Skills.
Plus check out: Healthy Risk-Taking; Benefits of Outdoor Play.

My children are all neurodiverse – autistic and/or ADHD, so I have lots of additional resources on neurodiversity: Accessing Developmental Testing; Meltdowns; Stimming; Autism 101; the Race Car Brain; Autistic? ADHD? SPD? Or Just “Quirky”?
I’ve got lots more info to check out: just click on a category name in the sidebar / links at the bottom of the page, or use the search bar.