"Justified True Belief" is a traditional theory of knowledge that suggests for someone to know something, three criteria must be met: the belief must be true, the person must believe it, and there must be justification for that belief. This means that simply believing something is not enough; it must also be accurate and supported by evidence or reasoning. Philosopher Plato is often associated with this concept, as he discussed it in his dialogues. However, the theory faced challenges, particularly from Edmund Gettier, who presented scenarios where these criteria could be met without genuine knowledge, leading to ongoing debates in epistemology.