Different methods are used to describe the coupling between the quantum and classical subsystems. In mechanical embedding, the quantum-classical interactions are treated purely classically, whereas, in electrostatic embedding, the classical subsystem is allowed to polarize the electron density of the quantum subsystem by including the electrostatic potential from the force-field charges in the Hamiltonian of the quantum subsystem. Polarizable embedding (PE) includes, on top, also a polarizable environment, thus enabling mutual polarization between the quantum part and its classical environment. In the induced point dipole formulation of PE, the polarization of the environment is represented by induced dipoles calculated from isotropic or anisotropic dipole-dipole polarizabilities. The induced dipoles are determined self-consistently with respect to the electron density of the quantum subsystem. The quantum subsystem is thus embedded in the potential from the permanent charges, or electric multipoles in general, and induced dipoles. Therefore the environment potential is often referred to as the embedding potential.