The word science includes both the scientific method for deriving knowledge and the body of scientific knowledge so derived. The scientific method is a systematic, objective technique for fact finding and fact checking based on observations and logical deduction that can be independently verified and is thus self-correcting.
We pursue science in an effort to understand how things in nature work, how they may change in the future, and how we can best adapt to living more successfully and safely with nature both now and in the future.
Scientists observe things that happen and develop theories about what caused them to happen. Over time, as a new theory explains more and more observations in increasing detail, scientists begin to think that this theory is more likely to be correct. Scientists understand that we are unlikely ever to be 100% sure and know that many well-established theories in the past have not stood the test of time.