scientific law predicts the results of certain initial conditions. It might predict your unborn child’s possible hair colors, or how far a baseball travels when launched at a certain angle.
In contrast, a theory tries to provide the most logical explanation about why things happen as they do. A theory might invoke dominant and recessive genes to explain how brown-haired parents ended up with a red-headed child, or use gravity to shed light on the parabolic trajectory of a baseball.