Bloom's taxonomy is a classification system used to define and distinguish different levels of thinking skills. It categorizes cognitive, affective, and sensory domains of learning. The cognitive domain involves knowledge and mental skills like remembering, understanding, applying, analyzing, evaluating, and creating. Lorin Anderson and David Krathwohl later updated the cognitive taxonomy to include remembering, understanding, applying, analyzing, evaluating, and creating knowledge at different levels from factual to metacognitive.