Modeling is a measure of our understanding of processes and a tool for checking hypotheses and making prognoses. Any attempt to understand and explain electromyographic (EMG) signals, their characteristics, and changes is related to modeling. The authors’ aim is to present the main ideas of EMG modeling in terms understandable to people without special mathematical education. The main physical regularities that rule the formation of electrical potentials in a volume conductor (extracellular medium) are pictorially demonstrated and can be realized ignoring equations. Potentials produced by individual muscle fibers are the basis of EMG signals, which is why a more detailed picture of the physical basis for modeling single-fiber potentials (SFPs) generated in a homogeneous volume conductor of infinite extent is presented. It is demonstrated why the shape of SFP changes with distance from the active fibers, why amplitude of EMG signal can be an unreliable characteristic, and why detection of EMG by needle and surface electrodes has different sensitivity to prolonged phase of repolarization or to after-depolarization in intracellular action potential (IAP) and to IAP propagation velocity along the fiber. Description of some equations resulting in fast calculation of the motor unit potentials and interference EMG are presented. The latest papers on mathematical modeling that take into account inhomogeneous and restricted muscle tissue are discussed.