Roughly half of all the stars in the Universe are known to be in binary or higher order
multiple systems. Moreover, the binarity is strongly correlated to the mass, with almost
~100% of massive O stars being born in binary systems. Since these massive stars are the
progenitors for many high-energy astrophysical phenomena including supernova explosions,
gamma-ray bursts, X-ray binaries, gravitational waves, etc, it is crucial to understand
how such stars evolve in binary systems in order to understand their origin. In this
talk I will review the basics of stellar and binary evolution theory, as well as some of
the latest developments. In particular, I will highlight the different numerical
techniques used to tackle stellar/binary evolution, as well as their scope and
limitations. In the remaining time I will also introduce some of my own contributions to
the field, on topics including common-envelope evolution and wind-accretion onto black
holes.