The videos were really helpful- Thanks!  So it is basically just a way of grouping and using it more efficiently.  Good to know!

Len,
 
Depending on the situation, I've used as few as 4 and as many as 24 buses. The more tracks a song has, the more likely I am to use more buses. 
 
Sometimes all the drums will go into a Drum Bus. Other times, with more than one track, the kick tracks will go to a Kick bus, which will then go to the Drum bus, which then goes to an Instrument bus, which then goes to a Master Sub bus, which then is split into a Low bus and a High+Mid bus (got this from one of Craig Anderton's videos. Works AWESOME BTW. Thanks, Craig!!!), which then goes to the Master bus.
 
I also use buses for FXs.
 
....... or I might just send them all to the Master bus!!  LOL
 
I do like mixing with buses though.

I use buss to differentiate it from something one would take to go some place (a city bus). The first time I came across the term it had the two s's and was describing a personal computer before IBM and Apple jumped into the fray. It was a standard for building small computers. There was no motherboard just a buss that could take cards with various components like the CPU and input and output systems. 
 
I do not think it is a misspelling or a typo. However, I could be very wrong. None the less, I will continue to use the double s spelling.   
 
Now to answer the OPs question.  You have it correctly understood. A buss is a sub group that can be used for grouping like instruments for easy adjustments or for use as auxiliaries with sends and returns. Really, because the busing in Sonar is very flexible it can be used pretty much any way you may wish to.  
 
I like to have a drum buss at the bare minimum.  Then I might use an instrument buss too. I may add a vocal buss or solo buss. And so on. All those will go to the master buss and it will go to the main outs. 
 
 

Jlien X
I wonder why it's called "bus" (nothing to do with the vehicle, I hope). And I wonder why some posters mistakenly spell it "buss."

Actually, I remember it being spelled with two esses (buss) when I first saw the word written back in 1979. It's the single ess version that's looks wrong to me.
I'm sure it was originally an electrical term spelled 'buss,' but I can't prove it. All references now available seem to accept both spellings.

I'm with Ron. I was always told (by whom I can't remember) that "buss" is the correct spelling for audio busses. I believe it originates from electronics and thus mixing desks and like many terms continues in the digital age.
 
I always thought that it was just one of those Brit/US spelling differentials.

I get it. Buses are designed to carry many passengers, so if you think of a bus as carrying many tracks you are on the right road. (see what I did there)!!

I typically have the following busses:
 
Master
 
Reverb
 
Delay
 
OH
 
Toms
 
Drums (though certain drums havetheir own busses as indicated above, I sum them into another dedicated buss before sending to Master Buss)
 
Drum side chain buss (this will often be heavy compression to mix in with the other drum signal)
 
Acoustics
 
Backups (gives you control over the mix of the background vocals so that you only have to deal with one track).
 
LV (why not just put all the FX and sends on the LV track instead of a buss? Because often there are 5 takes, so that would mean using the same set of FX on all the 5 takes of the lead vocal-thus 5 compressors, eq's, de-essers, etc.
THis may beg the question--why don't you just make one composite track of all the takes? Well, I do that, but even when choosing takes I like to have the processing power availability because you get a good idea what the final is going to sound like. Often a take that sounds weak may be the best take if empowered with a bit of processing.)
 
And if it is a larger project, I will often have bounced down some of my big synth tracks such as Omnisphere, Storm Drum, etc. and group the high synths, low synths, into different busses.
 
 
 

It may have come from the word 'Busbar', which is an electronics/computing term.
 
busbar (ˈbʌzˌbɑː)

— n
1. an electrical conductor, maintained at a specific voltage and capable of carrying a high current, usually used to make a common connection between several circuits in a system
2. a group of such electrical conductors at a low voltage, used for carrying data in binary form between the various parts of a computer or its peripherals
 
 
The above would be my guess.
 
Bob Bone
 

Jlien X
I wonder why it's called "bus" (nothing to do with the vehicle, I hope). And I wonder why some posters mistakenly spell it "buss."

I like to think of it as a vehicle for audio going from one place to another inside of your DAW 

I always thought it was 'bus'. I was under the impression that 'Buss' was a branding name used by Bussmann, a leading manufacturer of Bus bars and Fuses that are sold under the terms "Buss bars" and "Buss Fuses". A bus bar is used to branch off electrical power and a bus fuse was used to provide overload protection. Now a days we use busses and circuit breakers instead of fuses so the usage has been dying out. Though older buildings whos electricals haven't been updated still use either the screw in types, or the snap in barrels.

In audio its the same. The output of several channels were physically attached to a bus bar. Then another channels input was also attached to tap the summed signal.

That channel was the bus channel, and I believe Bussmann's "buss bars" were used, you ended up with the odd spelling.

Sort of the way we call self adhesive bandages "band-aids" even though it is a name of a brand, not a type of product.

I may be a bit off but this is what I sorta remember. :)