Any number of statements may be true concerning scientific theories. The important thing to keep in mind when discussing a scientific theory, whether it is the theory of evolution or the theory of relativity, is that theory is not synonymous with hypothesis.
A hypothesis is a question or an idea that a scientist tries to answer by performing an experiment. If the data derived from the experiment is compelling enough, the hypothesis becomes a theory.
Scientists accept theories as adequate explanations for phenomena. This is in stark contrast to the use of the word "theory" in a non-scientific sense. In a non-scientific sense, theories are unproven ideas, and the word is defined very similarly to hypothesis.