In this review, several types of plasma electron sources, studied in the Plasma Physics and Pulsed power Laboratory during the last 20 years, are considered. Namely, main parameters, such as plasma density and temperature, expansion velocity and plasma uniformity, life-time and vacuum compatibility of passive plasma cathodes (explosive emission cathodes, metal ceramic, velvet, carbon fiber with and without CsI coating, carbon capillary, and multi-capillary and multi-slot) and active plasma cathodes (ferroelectric and hollow anodes) are described and discussed. These parameters were studied and characterized using different timeand space-resolved electrical, optical, spectroscopic, Thomson scattering, Laser Induced Fluorescence and Xray diagnostics. It was shown that the operation of passive sources is governed by the formation of flashover plasma whose parameters depend on the amplitude and rise time of the accelerating electric field. In the case of ferroelectric and hollow-anode plasma sources, the plasma parameters are controlled by the driving pulse and discharge current, respectively. In addition, parameters of high-current electron beams generated in high voltage and high current electron diodes with these plasma cathodes are presented.