Google Maps - Overlays
Overlays are objects on the map that are bound to latitude/longitude coordinates.
Google Maps has several types of overlays:
Marker - Single locations on a map. Markers can also display custom icon images
Polyline - Series of straight lines on a map
Polygon - Series of straight lines on a map, and the shape is "closed"
Circle and Rectangle
Info Windows - Displays content within a popup balloon on top of a map
Custom overlays