In addition to showing all the roads within Stilwater or Steelport, it also dipsplays many geographic features such as rivers and ridges, as well as buildings. While these are not perfectly detailed, these are good visual aids.
The Map has many functions of a modern GPS device, including adding a bookmark at any location, or setting a destination, which is referred to as a "waypoint". The route to the waypoint will be shown on the Map, as well as the mini-map shown on the on-screen HUD. As you drive around Stilwater or Steelport, you can unlock many "GPS Shortcuts" by driving down alleyways, pedestrian walkways and across empty lots.
The Map shows the name of the District and Neighborhood currently centered on the map, as well as markers for stores, activities, cribs, missions and strongholds. It can be set to display each of these categories separately, or all at once.
In certain underground locations, the Map will show the current area, but these underground maps are not accessible unless you are in that area. The Stilwater Caverns and Rounds Square Shopping Center for example, are multi-map underground areas, but you can only access a map of the current section you are in, which makes navigation difficult.