An overview of gravitational waves : theory sources and detection Theory of gravitational waves Alexandre Le Tiec Jérôme Novak Gravitational wave sources Monica Colpi Alberto Sesana Theory of gravitational wave detection Jean Yves Vinet Present and future ground based detectors Giacomo Ciani and Paul Fulda Laser interferometric space based observatories Guido Mueller LISA pathfinder Rita Dolesi Pulsar timing array Antoine Petiteau Future gravitational wave detectors based on atom interferometry Remi Geiger This book describes detection techniques used to search and analyse gravitational waves (GW). It covers the whole domain of GW detection starting from the theory and ending with the experimental techniques (both present and future) used to detect them. The theoretical sections of the book address the theory of GW in the general relativity followed by the theory of GW detection. The different sources of GW are described as well as the methods used to analyse them and to extract the physical parameters of the sources. With the recent announcement of gravitational wave detection and the first results from LISA Pathfinder this book will allow non specialists to understand the present status of the field and the future of gravitational wave detection