Specifically, a
lecture, illustrated by a series of
travel slides, or a narrated travel
film. This definition can be expanded to include travel journals, or just about any record of travel. In any case, all travelogues involve some sort of
narrator.
A travelogue may serve as a guide, but differs from the standard guide book style in that the purpose of a travelogue is to recount previous travel experiences, not to help a person plan a trip.
Also: "travelog."