Confused when to use routes vs tracks

I am new to Basecamp and am confused as to when to use a route or a track.  

I have a GPX file for a long trip I am breaking up into roughly 70km segments,  Where necessary I need to alter the routes so each segment is in a town.  This means while 99% of the route/track is present when I import it, I need it to create directions for the last 1%.

If I add points in a track, I get a straight line which is not what I want.  So should I be using a route?  As far as I can tell when I import the GPX file and don't change it, there is no difference.

This is probably obvious, but when I first open the the GPX file, I couldn't split it.  when I imported it it gave me a track and I could split it.  When I converted a track to a route, I then could not split the route.  So do I need to spit it up first, then convert to a route, then adjust where needed?

Thanks.