The marker tool is a simple marker pin placed on the map. This would be used for a single, precise location. Select the Marker tool, then select anywhere on the map to place the marker.
The polygon tool allows you to mark out a complex area. This entire area within the marked area is considered the location, and will be shaded on the map. Select the Polygon tool, then select points outlining the desired location on the map. To complete the polygon, select the starting point to close the shape.
This tool is good for displaying boundaries, that don't necessarily include the entire area within a shape for a particular location. For example, this can be a transportation or parade route. Select the Polyline tool, then mark the path of the desired location. This does not need to be a closed shape.
A circle, which can be used to display locations or zones that are best marked with a circle. Any location with an equal distance to it's boundaries should be shown with a circle, such as the range of a wifi signal. Select the Circle tool, then select on the map and expand the circle until desired. Select the square in the middle to move the circle, or the single square on the edge to increase/decrease the size.
This is a simple rectangle/square shape, includes the area within the shape for the location. Select the Rectangle tool, then mark the desired area. Select and drag the middle square to move the shape, or one of the outer squares on the corners to resize.
The Polymarker tool is a location that contains multiple precise locations, such as restrooms around campus, or possibly bus stops. Select the Polymarker tool, then select all locations within that single location.