my nutshell model of hippocampal formation is this:
entorhinal cortex (EC) encodes generalized dimensional structures / types of relations via grid-cells & object-vector-cells, and hippocampus maps specific (sensory, abstract) cues onto those relations, thereby making place-cells, landmark-cells, splitter-cells, etc.
iow, EC is where abstract math is stored when it's deeply intuitive, and hippocampus is the thing that *applies* those mathy relations to practical stuff.