This paper focuses upon the many functions that are served by evaluations, and by the process of conducting them. Many forms or types of evaluation have evolved to serve these different functions; and a brief account is given of some of the most common of these forms and the issues or controversies that they have engendered. The discussion opens, after a brief historical note, by describing the differing views of Lee Cronbach and Michael Scriven about whether an evaluator should aim to educate stakeholders about the program so that they can make informed decisions about it, or whether evaluators should go further and make a value judgement about it. The discussion then moves on to the importance of not overlooking the unintended effects of a program that is under study; and after presenting a list of functions that evaluations can have, the remainder of the discussion deals with the "pros" and "cons" of, and the differences between, formative and summative evaluations.