  Smoothed Particle Hydrodynamics is a multidimensional Lagrangian method of
numerical hydrodynamics that has been used to tackle a wide variety of problems
in astrophysics. Here we develop the basic equations of the SPH scheme, and we
discuss some of its numerical properties and limitations. As an illustration of
typical astrophysical applications, we discuss recent calculations of stellar
interactions, including collisions between main sequence stars and the
coalescence of compact binaries.
