trackpoints
waypoints
routepoints
viapoints
Each has different uses and much different limits.
I think there is a lot of slack terminology - on Garmin's part as much as anyone else's.
Given that a 'waypoint' is just a pair of co-ordinates in a wrapper, all the others are just variants and you can add to the list, map points, POIs and geocaches. They are all information-rich to a greater or lesser degree which might help explain why there are diffierent limits on different types.
The oft-quoted and misquoted 'waypoint limit' refers to what are best described as 'user waypoints' which have the potential to be very information-rich indeed.
The trackpoint limit of 500 on a saved or uploaded track is indeed ridiculously low, given that trackpoints are very simple points. On a card-carrying model you can daily-dump the tracks to card which is not subject to the 500 limit. The active track limit of 10,000 is not the default out of the box - it comes set to something like 3000 but you can raise that in the menus.