Bloom's taxonomy is a classification system used to define and distinguish different levels of human cognition. It was originally developed in 1956 by Benjamin Bloom and was later revised in the 1990s. The revised version exchanges the top two levels - Creating is now the highest level followed by Evaluating, while the lower levels remain Analyzing, Applying, Understanding, and Remembering. The taxonomy provides verbs for each level to describe cognitive processes, with the updated version using verbs rather than nouns.