Microvillus
On a tongue, the microvilli are the tiny hairs on the taste buds that send signals to the brain.  These signals are interpreted by the brain, and tells the brain what things taste like. Over time, as a person tastes more and more things, the brain stores the information the microvilli send in a databank of information.  This databank is used to compare new tastes to old tastes, and help to classify them by comparing and contrasting their qualities.