As you begin to better shape your hand, you will most likely be adding additional edge loops. A few common scenarios are controlling rounding, shaping details, and flattening the base.
Adding extra edge loops
Controlling rounding
As we have seen, the Subdivision Surface Modifier rounds and smooths things out. There are cases, however, where we would like to have better control of the rounding. An example in this model is the right side of my hand. It initially has a very flat feel. Doing a Loop Cut and Slide down the cross-section of the entire hand gives me extra control to start to round those areas out:
Adding an extra edge loop provides extra vertices to round out the side of the hand
I also add extra edge loops down...