The mechanism responsible for the generation of the mass of an particle has emerged as one of the most urging questions in fundamental physics. The effective-theory approach provides the theoretical basis for a model-independent description of the effects sensitive to this mechanism and their impact on observables. This book systematically develops this method, relating the predictions of different physics scenarios in a unified treatment. It also contains a detailed discussion of the processes that can actually be observed, the status of calculations, methods to isolate the interesting signals, and expectations for the sensitivity of future collider experiments. The systematic bottom-up approach provides the appropriate framework for interpreting measurements that will be performed to better understand the physics of mass generation in the universe. No knowledge of quantum field theory is required other than familiarity with effective Lagrangians and Feynmann diagrams. This book will be useful for both theorists and experimentalists who are interested in the phenomenology of electroweak interactions.