I am reading Pekar's "Research in Electron Theory of Crystals" and I came across a passage I find a bit unclear:
The theory developed below takes into account the dielectric polarization of a an ionic crystal by the electric field of the conduction electron. The local polarization that results from this is related with the displacement of the ions and consequently is inertial. It cannot follow the relatively rapidly moving electron and therefore forms a potential well for the electron. The depth of this potential well turns out to be sufficient for discrete energy levels of the electron to exist in it. The electron, being in a local state on one of these levels, can maintain with it sown field the aforementioned local polarization of the crystal. Because of their inertia, the ions are sensitive not to the instantaneous value of the electron field, but to the average field. The latter can be calculated as the static field of the $|\psi|^2$ cloud of the electron; it produces a static polarization potential well, which in turn maintains the electron stationarily in a local state. Such states of the crystal with the polarization potential well, which in turn maintains the electron stationarily in the local state. Such states of the crystal with a polarization potential well, in which the electron is localized, were called by the author polarons
Now, what exactly does he mean by local vs. conduction electrons? Are local electrons those that are not moving and are in the crystal? That doesn't seem right. What does it mean for an electron to be in a local state? (Also what does he mean by "inertial"?) IN fact, it would be nice if one explains this passage in understandable terms so that I can have some intuitive picture in mind.