A scientific theory supported by facts is called a Scientific law.
The process starts at the observation of a phenomena and uses scientific methods. A hypothesis is formed to explain the observations and is tested. If repeated testing (and modifications) support the hypothesis (time and again), it is called a scientific theory. The theory has to stand the test of time and can be tested any number of times. Each successful testing increases our confidence in it, while each failure brings it into question. Kindly note that theories can always be revised or unified to explain the observations or phenomena. With enough supporting evidence, a scientific theory can be elevated to the status of scientific law. A law may be applicable only under certain set of conditions and hence one should be careful in their application.
Some of the universal laws include conservation of mass and energy, Newton's laws, etc. (although they may also fail under exceptional circumstances).
Hope this helps.