What do the triangles represent on a topographic map. A mountain peak. B location of a ravine. C steepness of a slope. D distance between two areas.

Are you asking about a street map usage  if so here is your answer  a street map for a very limited area could simply be a bit map or a .jpg image.  but a more general map would probably store the streets as vectors.  but you shouldn't assume that there is one way to do it