You are swimming in a shallow pond. You touch the bottom of the pond with your foot and feel a hard rock. You dive down to collect it. What type of rock have you most likely
found?

Giga is the second highest prefix on the normal scale, the first is terra.

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