What can be learned about marketing phenomena from descriptive, structural, and experimental empirical models? Is structure implicit in a descriptive empirical model? What is a "reduced-form model?" What is a natural experiment, and what can one infer from a study that uses experimental data? Having clear answers to these questions can improve empirical dialog. This paper defines descriptive, structural, and experimental empirical work, provides examples, discusses their similarities and differences, and comments on their strengths and weaknesses. An important theme is that the marketing question and the data available should determine the methods used, and not the other way around. Most of the examples discussed reference linear models that are widely employed in the marketing literature. Many of the points, however, extend to the development and interpretation of cutting-edge nonlinear, dynamic, or nonparametric models used in marketing.