  Particle velocity distribution functions (VDF) in space plasmas often show
non Maxwellian suprathermal tails decreasing as a power law of the velocity.
Such distributions are well fitted by the so-called Kappa distribution. The
presence of such distributions in different space plasmas suggests a universal
mechanism for the creation of such suprathermal tails. Different theories have
been proposed and are recalled in this review paper. The suprathermal particles
have important consequences concerning the acceleration and the temperature
that are well evidenced by the kinetic approach where no closure requires the
distributions to be nearly Maxwellians. Moreover, the presence of the
suprathermal particles take an important role in the wave-particle
interactions.
