In this paper, we review phenomenological and physical-chemical theories of Induced Polarization (IP) of saturated ion-conducting rocks and soils. The IP phenomenology is based on a behavior of equivalent electrical scheme including parallel connection of two elements: (1) a resistance, and (2) a serial connection of another resistance and capacitance. This scheme can be described based on a very popular Pelton [1978] model. Then we review two classes of physical-chemical theories, describing the granular and the capillary models of rock/soil. Both are based on the theory of Electrical Double Layer (EDL) occurring at the interface between the solid and liquid phases. In the granular model IP is mostly produced by the polarization of the inner part of EDL (the Stern layer), and in the capillary model – by the membrane polarization, which, in turn, is closely related to polarization of the outer part of EDL (the diffuse layer). In conclusion, we address two methodological principles of IP modelling: (1) experimental determination of a dominant IP physical mechanism typical of each rock/soil type, and (2) theoretical modelling of such a mechanism using minimally needed measurable parameters.