Motor development is not a single line from helpless to capable. It runs on two parallel tracks: gross motor (big movements) and fine motor (small, precise movements). Both tracks are developing simultaneously, but they progress at different rates and follow different patterns.
Gross motor development follows a head-to-toe sequence. Your baby gains head control first, then learns to control their trunk (rolling, sitting), then their legs (crawling, standing, walking). Fine motor development follows a center-to-periphery pattern. Your baby first controls their shoulders, then their arms, then their hands, then their individual fingers. This is why babies swipe at objects before they can grasp them, and grasp with their whole hand before they can pinch with two fingers.
Understanding these two tracks helps you notice what is developing well and what might need attention. A baby who is walking on time but not picking up small objects might benefit from more fine motor practice — or might need an evaluation for occupational therapy. A baby with great hand skills who is not yet crawling might just need more floor time and tummy time.