The concepts are quite simple. It's the method of distinguishing one from the other that is likely quite subtle in the code.
POI - A formal Point Of Interest. An entry in the internal POI database with a name, location and usually other information associated with it.
Waypoint - Any arbitrary point on the map that you have designated you want to keep track of. Usually stored in the "Favorites" or "My Locations" or whatever your personal navigation device calls its waypoint storage database. Your device will usually allow you to store such things as the location, any arbitrary name you want to supply and other information such as address, phone number, category(ies) and a symbol/icon to be used when displaying it.
Via Point - A point used to create a multipoint route, e.g. Go from Point A to Point B via some other arbitrary point(s) that you will designate. If your personal navigation device supports multipoint routing, the via point can be a POI, an existing waypoint/favorite or any other form of location that is searchable on your device, e.g. address, intersection/junction, custom POI, etc. In most cases, to use something as a via point it must already exist in one of the devices' searchable databases.
Shaping Point - In Mapsource, to "shape" a route to go exactly where you want there are a couple of methods. Just as with the personal navigation device, you can edit the route's properties to insert Via points (these are not shaping points although they do serve a similar purpose). You can also just use the route tool to click on spots on the map to force the shape of a route. When you do that, you are using a location that is not already in one of the searchable location databases. Mapsource does not force you to add these points to any of the formal databases. It simply inserts the actual coordinates invisibly into the route. These are shaping points.
Shaping points occur in another, automatic, fashion as well. Even when you only designate a two-point route, e.g. go from Point A to Point B, there will usually be multiple places, usually intersections, where a change in direction is required. When building the route, the personal navigation device (or Mapsource/Basecamp) will automatically include all of these points in the route.
To easily illustrate this, you can create a two-point route in Mapsource by clicking on a Point A and a Point B that will require a few turns to get from one to the other. Now export the route to a GPX file and take a look at it with Notepad or your favorite text editor. You will see that, in addition to the starting point and the ending point, there will be a bunch of other points <rtept> in the file to control all the turns.
I apologize if you already knew all that. Perhaps it will be helpful to others with inquiring minds. :)
...ken...
