Falsifiability is a principle introduced by philosopher Karl Popper that suggests a theory must be testable and able to be proven false to be considered scientific. This means that for a hypothesis to hold scientific merit, there must be a possible observation or experiment that could show it to be incorrect. In essence, falsifiability distinguishes scientific claims from non-scientific ones. For example, a statement like 'All swans are white' can be tested and potentially disproven by observing a black swan. This criterion helps ensure that scientific theories remain open to scrutiny and revision based on new evidence.