The difference between courses and routes on a gps cheers

Strictly speaking a 'course' is the same as a 'heading', meaning the direction you are currently going in.

A 'route' is a number of waypoints linked together to create series of headings. These normally connect significant trail features such as mountain tops, river crossings or the pub at the end, although they can of course be programmed for any grid refernce. Typically more information can be assigned to waypoints, such a name etc.

There is another term, 'track', which a series of 'trackpoints'. These are purely grid reference markes which when linked together create a more detailed path or route to follow. Trackpoints tend not to have names assigned or any other attributes, hence most GPS units can store many more trackpoints than waypoints. A GPS can be set to log trackpoints at regular intervals to provide a record of where you have been. Typically these 'tracklogs' can be downloaded into mapping software for displaying on a computer.

If this is on something like a Garmin Edga, a Course will have timestamps associated with it which allows some extra computation to take place. A Route does not have this.

If you have a Garmin Edge 705 then a course (.crs) is what you need if you want to load in a trail and then follow it.

Routes tend to have a limited number of waypoints that can be stored whereas you can keep dozens of long courses in there.

There's a bunch of free software out there to convert mmo files to gpx to crs etc.

In that context then, a 'course' would seem to be the same as a 'track' on other Garmins (the E-Trex for example)

I'm not sure. Garmin temselves seem to be confused. In Training Centre, History used tcx files and Courses use crs (Garmin Course Database Files).