The Lambda Calculus is a formal system, originally intended as a tool in the foundation of mathematics, but mainly used to study the concepts of algorithm and effective computability. Recently, the Lambda Calculus and related systems acquire attention from Computer Science for another reason too: several important programming language concepts can be explained elegantly and can be studied successfully in the framework of the Lambda Calculi. We show this mainly by means of examples. We address ourselves to interested computer scientists who have no prior knowledge of the Lambda Calculus. The concepts discussed include: parameterization, definitions, recursion, elementary and composite data types, typing, abstract types, control of visibility...