In its broadest sense, anatomy is the study of the structure of an object, in this case the human body. Human anatomy deals with the way the parts of humans, from molecules to bones, interact to form a functional unit. The study of anatomy is distinct from the study of physiology, although the two are often paired. While anatomy deals with the structure of an organism, physiology deals with the way the parts function together. For example, an anatomist may study the types of cells in the cardiac conduction system and how those cells are connected, while a physiologist would look at why and how the heart beats. Thus, anatomy and physiology are separate, but complimentary, studies of how an organism works.
A complete article on the history of anatomy can be found here.