Final answer:
Natural Concepts are formed from direct or indirect real-world experiences and lack an exact definition, as opposed to artificial concepts which have a specific set of characteristics.
Step-by-step explanation:
Concepts people form from their real-world experiences and that lack an exact definition are called Natural Concepts. These concepts are developed through direct or indirect experiences with the world around us. For instance, someone living in Essex Junction, Vermont, may have a well-developed natural concept of snow due to direct experiences with different types of snowfall. Natural Concepts contrast with artificial concepts, which are understood by a fixed set of characteristics, as seen with geometric shapes like triangles and squares in mathematics.