Track : A collection of Trackpoints, listed in the order which they were written. It is usually displayed as a wavy line
(a collection of segmented straight lines that connect two neighboring Trackpoints which were listed in order).
A Track always has a starting Trackpoint and ending Trackpoint since it is written in order.
There can be multiple tracks on a map.
Direction of a Track : A track always has a direction from the starting Trackpoint to the ending Trackpoint.