The manuscript is organized as follows. First, in the following section, we review the formalism connecting charge density profiles, electrostatic potentials, and electric fields. Then, in Sec. III we provide a brief review of the experimental, theoretical, and computational studies that have led to our current understanding of the interfacial electrostatic environment. In Sec. IV we present the details of the simulation model. We use this model to explore the properties of the interfacial potential, presented in Sec. V, and interfacial electric fields, presented in Sec. VI. Finally, in Sec. VII, we conclude and comment briefly on the scientific outlook of this field.