A fact in science is something that can be proven by observation (seeing something with your own eyes) or measurement (using a tool, a ruler, scale, stopwatch to see differences that you cannot find very easily.
It is common misunderstanding to confuse the fact with someone’s opinion. Opinion is simply something a person may like or dislike based on his/her values.
There are several stages in a scientific method which includes, facts, inferences, hypothesis etc. Once gone through all the procedure, a scientific method can be established.