Multiparticle production is the most characteristic feature of current high-energy physics. Today, observed particle multiplicities are typically between ten and a hundred, and with future machines this range will be extended upwards. The bulk of the multiplicity is found in jets, i.e. in collimated bunches of hadrons (or decay products of hadrons) produced by the hadronization of partons, i.e. quarks and gluons. (For some applications it will be convenient to extend the parton concept also to some non-coloured but showering particles, such as electrons and photons.)