  This Chapter provides a brief tutorial on some aspects of plasma physics that
are fundamental to understanding the dynamics and energetics of the
intracluster medium (ICM). The tutorial is split into two parts: one that
focuses on the thermal plasma component -- its stability, viscosity,
conductivity, and ability to amplify magnetic fields to dynamical strengths via
turbulence and other plasma processes; and one that focuses on the non-thermal
population of charged particles known as cosmic rays -- their acceleration,
re-acceleration, and transport throughout the cluster volume. Observational
context is woven throughout the narrative, from constraints on the strength and
geometry of intracluster magnetic fields and the effective viscosity of the
ICM, to examples of radio halos, radio relics, and cluster shocks that can test
theories of particle acceleration. The promise of future X-ray missions to
probe intracluster turbulence and discover the impact of small-scale plasma
physics, coupled with sensitive, high-resolution radio observations of
synchrotron-emitting plasma that reveal the properties of intracluster magnetic
fields and particle-acceleration mechanisms, are likely to establish galaxy
clusters as the premier cosmic laboratories for deciphering the fundamental
physics of hot, dilute plasmas.
