  Some of the oldest and most important applications of thermodynamics are
operations of refrigeration as well as production of useful energy. Part of the
efforts to understand and develop thermodynamics in the quantum regime have
been focusing on harnessing quantum effects to such operations. In this review
we present the recent developments regarding the role of quantum coherences in
the performances of thermal machines --the devices realising the above
thermodynamic operations. While this is known to be an intricate subject, in
part because being largely model-dependent, the review of the recent results
allow us to identify some general tendencies and to suggest some future
directions.
