The way I understand it, though like almost everything in life there is bound to be exceptions, a law is an observed principle. Such as the law of gravity that states when you drop any object with mass on an Earth massed and sized object, it will (discounting air resistance) attempt to accelerate to the center of the object at about 32 feet per second per second. If you have the same starting conditions, you will get the same results.. An hypothesis is an attempt at explaining the results. What IS gravity, what is it that makes things with mass accelerate to the center of an Earth sized and massed object at about 32 feet per second per second, what gives things mass PERIOD? A theory is an hypotheses that experiments have shown to be consistent with the way the world works as known at the time. Such as the theory of relativity as an explanation of gravity.
Over time observations are made that are inconsistent with the predictions of the theory, and so scientists start thinking of a new theory that a) explains everything the old one explains, b) explains the new observations and hopefully c) predicts new observations that scientists attempt to observe.
Please correct any errors I have made here please.

[edit]Thank you hhEb09'1 for the corrections.

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