Whats the difference between aux, insert, and send busses?

Better question what are they and where are they in N-Track


Check out AudioMinds and Mixed Signals for general info on mixers.

That should give you a good idea about the functions of a mixer, which will translate over to how the mixer in n-Track works.
Any rate, an Aux channel, insert and Send bus are all for signal routing. They can serve a specific purpose or you can be creative with their uses.
n-Track doesn’t offer Send busses per se. You can however make use of the Aux channels or groups to create separate output busses provided you have a multi-output soundcard.
There is a great deal of info that can go into explaining all of the routing capabilities that can be created within n-Track (depending on the capabilities of your soundcard).
If there is something specific you would like to know or something you are trying to achieve, it would be easier to break it down to offer suggestions as to how you would best accomplish your needs.