A theory is a well tested, widely accepted explanation that combines several observations and hypothesis. A law is a statement about how something behaves or functions in the natural world. A law cannot be changed or replicated, and it is a factual statement. Theories are based on repeated experiments and experimental methods change. Sometimes these new methods provide new information and theories are changed or replaced.
A law is 100% proven while a theory is not. A law is never wrong while a theory, although widely accepted or has been tested hundreds to thousands of times, may be found incomplete or eventually wrong.