A hypothesis is an educated guess. This is part of the scientific method developed in science to explain natural phenomena in the environment. Usually scientists use the hypothesis in their controlled experiments.
Whether it is a fact or not scientists use the hypothesis as a basis or a starting point for further explanations. This is known as the scientific hypothesis. When an educated guess yields the same results over time, the answer is called a theory. Something that is widely accepted but still needs to be proven and investigated further.