Trackpoint : A pair of coordinates. It has to be part of a Track.
Trackpoints can be generated by the Track drawing tool and/or by a moving GPS (Ramblr App) as a “breadcrumb trail”.
A Trackpoint generated by a moving GPS (Ramblr App) has a timestamp and 3-dimensional coordinates including elevation.
However, a Trackpoint generated by the Track drawing tool doesn’t have a time stamp.

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.