Multilevel inverters represent a high potential for realization of a high power controllable conversion system of different nature, rectifiers, inveters, high power amplifiers, etc. From the even more applied three-level inverter to the multiple AC stages VSI, different topologies are applied, withan increasing quanty of pssible levels. Usually, the theory of multilevel inverters is presented with different definition of the number o levels. The contrubution will give some logic definitions on basic schemes, and present the various versions of the technique of one and multiple-phase multilevel inverter systems.