The book reviews recent observations of non-evolved and evolved binary populations in clusters and the field with special emphasis on statistical biases, incompleteness and distribution functions. Different binary types are considered: cataclysmic variables, super-soft X-ray sources, double degenerate binaries, Algol-type binaries, Be binaries, X-ray binaries, and Wolf-Rayet binaries. The observational part ends with a discussion on stellar winds in massive stars, on new results of massive starbursts and on the characteristics and the rates of the different types of supernovae. Population synthesis relies on stellar evolution. Recent results on single star and binary evolution are presented. We then compare theoretical models of population synthesis to observations. Much attention is given at population dynamics, spectral synthesis of starbursts, number synthesis of the binaries and supernova rates discussed in the first part of this book. Finally, the book highlights the possible effects of binaries on galactic chemical evolution.