The difference between a theory and a law is that the law has been proven true so many times it is generally held to be one universal truth. The law of universal gravitation, commonly known as the law of gravity, works every time, with objects accelerating towards the Earth, with little difference in the outcome. Theories, on the other hand, are explanations of questions scientists have, but have not undergone the rigorous, extensive proving methodology laws have been subjected to. The theory of general relativity, published and put forth by Albert Einstein in the early 20th century, still is being tested and reviewed today. A hypothesis is, at best, an educated guess as to the outcome of a scientific experiment. Hypotheses do not always have to be correct; many important scientific discoveries have been made at the expense of a hypotheses being wrong.
Controlled conditions in a scientific experiment are the factors we don't think makes the difference in the outcome of the experiment. Therefore, we want to make sure those factors are the same in each experimental trial, to control them, so no one may say we changed them and that was what produced the results of our experiment.