What is the difference between buses and track?

In Sonar a track is where audio or MIDI resides. A buss is where a track outs too. The track is the container and the buss receives audio from it. All buses are the same. They are only different in the way they receive audio. A buss vs an auxiliary buss is an aux when it gets its audio from a track send or a send from another buss. A "normal" buss gets its audio from the output of an audio track. MIDI can not be sent directly to a buss. It must be turned into audio before it can go to a buss.  

To add to John's explanation, a buss is very useful if you want to control a group of similar instruments via a single fader - the obvious example being drums where you would balance the kit using the Track Faders
 
You would then set the outputs of all your drum tracks to a drum buss and then control the overall volume of the drums via the buss fader.
 
you can also add Fx at buss level.

Great information, Thanks guys.

You may want to try some tutorials like these:
https://www.groove3.com/sonar-training-videos
 
Cheers...

Busses do not run on tracks.
 
You are probably confusing them with trollies.

slartabartfast
Busses do not run on tracks.
 
You are probably confusing them with trollies.

Hihihi (Sorry to OP)

The primary difference between a track and a bus is that a track is a container for audio (or MIDI).
There are similarities in tracks and buses in that they both have mixing capabilities. Tracks can mix their inputs into the clip data on the track while buses mix the audio from all tracks or buses routed to them.
Multiple tracks can be routed to one or more buses to create submixes. Multiple buses in turn can be routed to other buses to sum them into another submix or the final output.
 
In a future build there will be fewer differences between tracks and buses since you will be able to freely route tracks to other tracks if you choose to do so.
 

In my humble opinion, you should route all your guitars to a guitar bus, vocals to a vocal bus, harmonies to a harmony bus, keys to a key bus, drums to a drum bus, etc. 
 
You should then route ALL of those buses to a Master Bus which dumps audio to your audio card (i.e., when you mute the Master bus, there is NO sound).
 
Why?  A whole slew of reasons. 
 
Number One is that you can turn off (mute) whole groups of instruments/vocals/harmonies, so that you can properly mix/fix other stuff. 
 
Number two is that you can put plugins on, for example, all the vocal tracks, by putting the effect on the Vocal Bus. 
 
Number Three is that you can use the Master Bus to [attempt to] master your whole mix with compression, EQ, etc.