This report gives a general survey of the production and properties of the jets of hadrons that are produced in high-energy collisions of elemenmy particles. Quarks and gluons, the constituents of hadronic particles, never appear directly; the closest one can get to their observation and study is through the jets of hadrons they produce in various types of experiment. The behaviour of these jets is described by the theory of QCD, the relevant points of which are summarized. The fragmentation of jets is understood in terms of various models, which are described. The various experimental variables used in the analysis of jets are critically compared, and used to present the experimental data. The production of jets in different experimental environments is described, and the results interpreted.