Anthropology can be defined as the holistic study of the human species. It searches for interrelationships among all the parts of its subject. Anthropology takes a four subfield approach: Biological (physical) anthropology, Cultural anthropology, Linguistic anthropology, and Archaeology. Data and concepts in each subfield have certain practical applications. These are collectively referred to as "applied Anthropology." Anthropologists all attempt to answer questions about the human species. Its central focus is the feature that is unique to humans—our cultural behavior. Culture is the way we as a species deal with our world and with one another. Understanding a species' behavior—even when that behavior is largely cultural—necessarily requires an understanding of all aspects of that species' identity, from its biology to its environment to its evolutionary past to the cultural behaviors that come in many different forms.