It is now clear that a binary evolutionary pathway is responsible for a significant fraction of all planetary nebulae, with some authors even going so far as to claim that binarity may be a near requirement for the formation of an observable nebula. This has led to the requirement that textbooks most likely need to be rewritten. Building upon the review of Jones and Boffin in Nature Astronomy (2017), this Springer Brief takes a first step in this direction. It offers the first expanded presentation of all the theoretical and observational support for the importance of binarity in the formation of planetary nebulae, initially focusing on common envelope evolution but also covering wider binaries. This book emphasises the wider impact of the field, highlighting the critical role binary central stars of planetary nebulae have in understanding a plethora of astrophysical phenomena, including type Ia supernovae, chemically peculiar stars and circumbinary exoplanets.