Jet physics in e+e- annihilation from 14 to 209 GeV

Results from the study of jets in hadronic final states produced in e+e- annihilation at sqrt(s)=14 to 209 GeV are discussed. Precise measurements of the strong coupling alpha_S at many points of sqrt(s) provide convincing evidence for the running of alpha_S as expected by QCD. Several measurements of the running b-quark mass m_b(M_Z) are combined yielding m_b(M_Z)=(2.92+-0.03(stat.)+-0.31(syst.)) GeV and compared with low energy results. Strong evidence for the running of the b-quark mass is found. Experimental investigations of the gauge structure of QCD are reviewed and then combined with the results for the colour factors C_A=2.89+-0.01(stat.)+- 0.21(syst.) and C_F=1.30+-0.01(stat.)+-0.09(syst.) and correlation coefficient rho=0.82. The uncertainties on the colour factors are below 10% and the agreement with the QCD expectation C_A=3 and C_F=4/3 is excellent.