The issue arises whether virtual particles can be considered to be "real" in the same sense that photons of light can be. So exactly when is a photon real and when is it virtual, and do virtual photons have as much right to be thought of as existing as "real" ones? A real photon (free field photon) is one that is propagating from one part of space to another without being in any way "anchored" to the originating charges, such as one coming from the Sun and going to your eye. A virtual photon is one that is in some sense anchored to a charge or charges. It may go directly from one charge to another, or return to the issueing charge if it isn't absorbed by another one. Real photons have four possible polarization states, and any admixtures of them. They can be vertically or horizontally polarized, or have right or left handed spin. By suitably adjusting the phases we can make any polarization state out of any other pair of states. The polarization refers to the direction of the electric field vector. Electric fields always act to change the momentum and energy of a charged body at the same time, while magnetic fields always act transversely on a moving body, i.e. at right angles to both the velocity and the magnetic field vector. To act otherwise would be to change the rest mass of the body, which Nature doesn't allow. Virtual photons can be longitudinaly polarized or have timelike polarization. They can't propagate very far from the source charge because the timelike and longitudinal amplitudes cancel out at long distances. Magnetic and static electric fields can be thought of as being made up of virtual photons, so they have as much right to being considered real as real photons do.