With ever-increasing growth in VLSI technologies the number of gates per chip area is constantly increasing, while the gate switching energy does not decrease at the same rate, so the power dissipation rises and heat removal becomes more difficult and expensive. Then, to limit the power dissipation adiabatic operation promises large reductions of power consumption because it does not dissipate energy. This paper reviews different types of adiabatic logic families. Adiabatic logic circuits working principle is discussed. Adiabatic switching and how it can be used to conserve power is discussed.