Development milestones give a rough map, not a strict rulebook — the range of "normal" at every age is wider than most milestone charts suggest. Here's a reassurance-first overview by age band.
Milestone charts can be a source of either useful guidance or unnecessary anxiety, depending on how they're used. The framework below is meant as the former — a general sense of what typically develops when, with the reminder that meaningful variation within these ranges is completely normal.
Two children can both be entirely typically developing while reaching the same milestone six months or more apart. Charts present tidy age brackets, but real development is genuinely uneven and individual — a child ahead in physical milestones might be right on track (or even behind) in language, and this unevenness within one child is itself completely normal.