What's the difference between fine motor and gross motor skills?
A motor skill is an action that involves the movement of muscles in your body. Gross motor skills are larger movements involving the arm, leg, or feet muscles or the entire body -- things like crawling, running, and jumping are gross motor skills. Fine motor skills are those smaller actions like picking things up between the thumb and finger or using the toes to wriggle into sand or the lips and tongue to taste and feel objects.
Gross motor and fine motor skills develop in tandem because many activities depend on the co-ordination of both sorts of skills. At 3 months you may notice your baby bringing his hands together over his chest as he lies on his back (a gross motor skill) and then playing with his hands (a fine motor skill). Even filling a shape sorter box, at about 18 months, for example, requires that your baby be able to use gross motor skills to hold his body steady enough to grasp the shapes firmly and fine motor skills to twist or turn each shape so that it fits into its appropriate hole.
You can encourage your baby to develop his fine and gross motor skills by watching to see how he uses his fingers, his arms, and his legs and then providing other opportunities for him to use his body in similar ways, perhaps with different toys or from a different position, which makes it slightly more difficult. A good activity is one which stretches your baby just a little. Your baby will find that developing his skills is more fun when he has a frequent change of position and activity. Let little and often be your mottor.