Critical Rationalism (CR) is the philosophy of Karl Popper. It has been misunderstood by many.
CR roughly says that knowledge is created through guesses and criticism of these guesses.
One common misconception is that people mistakenly equate falsification with CR.
Falsification, in a philosophical sense, is roughly the idea that you can formulate a specific claim (i.e. a guess) about something in such a way that certain observations could contradict the claim.
If observations turn out to contradict your claim, your claim is wrong.
Even though your specific claim is proven to be wrong, a similar claim could still be correct.
(Edit 2020-07-30: Theories can not be conclusively disproven as we could be mistaken, our instruments could be faulty, and for many other reasons.)
Falsification, usually done through experimental testing, is only one type of criticism among many.
Although falsification could be a part of CR, it is thus not central to Popper’s position.
(See my discussion tree “CR, Oism, what intelligent ppl do” on SubscribeStar for another example of how people mistakenly equate falsification with CR.)