A drug target is a molecule in the body, usually a protein, that is intrinsically associated with a particular disease process and that could be addressed.
A biological target is anything within a living organism to which some other entity is directed and/or binds, resulting in a change in its behavior or function. Examples of common classes of biological targets are proteins and nucleic acids.
Target identification and characterization begins with identifying the function of a possible therapeutic target (gene/protein) and its role in the disease. Identification of the target is followed by characterization of the molecular mechanisms addressed by the target.