  The following lectures are an introduction to the phenomena of partonic
saturation and nonlinear evolution equations in Quantum Chromodynamics. After a
short introduction to the linear evolution, the problems of unitarity bound and
parton saturation are discussed. The nonlinear Balitsky-Kovchegov evolution
equation in the high energy limit is introduced, and the progress towards the
understanding of the properties of its solution is reviewed. We discuss the
concepts of the saturation scale, geometrical scaling and the lack of the
infrared diffusion. Finally, we give a brief summary of current theoretical
developments which extend beyond the Balitsky-Kovchegov equation.
