  Turbulence is ubiquitous in the insterstellar medium and plays a major role
in several processes such as the formation of dense structures and stars, the
stability of molecular clouds, the amplification of magnetic fields, and the
re-acceleration and diffusion of cosmic rays. Despite its importance,
interstellar turbulence, alike turbulence in general, is far from being fully
understood. In this review we present the basics of turbulence physics,
focusing on the statistics of its structure and energy cascade. We explore the
physics of compressible and incompressible turbulent flows, as well as
magnetized cases. The most relevant observational techniques that provide
quantitative insights of interstellar turbulence are also presented. We also
discuss the main difficulties in developing a three-dimensional view of
interstellar turbulence from these observations. Finally, we briefly present
what could be the the main sources of turbulence in the interstellar medium.
