  We provide a general discussion on the importance of three-body Efimov
physics for strongly interacting ultracold quantum gases. Using the adiabatic
hyperspherical representation, we discuss a universal classification of
three-body systems in terms of the attractive or repulsive character of the
effective interactions. The hyperspherical representation leads to a simple and
conceptually clear picture for the bound and scattering properties of
three-body systems with strong $s$-wave interactions. Using our universal
classification scheme, we present a detailed discussion of all relevant
ultracold three-body scattering processes using a pathway analysis that makes
evident the importance of Efimov physics in determining the energy and
scattering length dependence of such processes. This article provides a general
overview of the current status of the field and a discussion of various issues
relevant to the lifetime and stability of ultracold quantum gases along with
universal properties of ultracold, resonantly interacting, few-body systems.
