Directions
Parameter 
Description 

ShowDistance 
Specifies whether to return the distance for the route.

ReturnRouteDirections 
Specifies whether to return turnbyturn directions for the route. This option is enabled by default.

ReturnSegmentGeometry 
Specifies whether to return a set of latitude/longitude points that represent a geometry for a segment within a route. The segment geometry is used to create the route geometry. The output of this field is shown within the RouteDirections output field. For more information about route geometry, see What is Route Geometry?. 
ReturnRouteGeometry 
Specifies whether to return a set of latitude/longitude points that represent a route geometry. The route geometry can be used to create a route map and to perform analysis on the route. One of the following:

DefaultLanguage 
Specifies the language in which GetTravelDirections should return directions. One of the following:

ShowTime 
Specifies whether GetTravelDirections should return the time it takes to follow a direction within the route.

ShowPrimaryNameOnly 
Specifies whether GetTravelDirections should return all names for a given street in the directions or if it should return just the primary name for a street.

What is Route Geometry?
A route geometry is a series of latitude/longitude points that form a route. A route geometry can be as simple as a single point, such as a route that starts and ends on the same street segment:
Since the starting point is always known the route geometry in this very simple example could be just the end point. So if A is the starting point, the route geometry could be the latitude/longitude of point B.
In a more complex route geometry involving multiple route segments there can be several points in the route geometry. Consider the route highlighted below which starts at point A and ends at point C, traveling through intersections X, Y, and B:
In this route, the full route geometry would consist of the latitude/longitude of points A, X, Y, B, and C. Note that you can control which points to actually return and may choose to include all points in the route geometry or just the end points of each route segment. In the above example, the end points are B and C, since A to B is one route segment and B to C is another.