I'm a noob and have been going over the RB Forum post by post to pick up questions I haven't even thought of yet. I keep seeing references to
"sending the mix to a buss" and wondered what that means. I'm guessing that it is somewhat akin to a clipboard where you can set plugins to affect multiple tracks at once rather than individually. If that is correct, how do I get there?

In RB quickest easiest way is to use the AUX Send and put the FX in the the AUX FX area (upper right of mixer screen).
There are 8 AUX busses available.
To send the track to a given buss, there is a dial on the mixer for each track.
If it is a MIDI track the dials are for Reverb, etc., but if it is an Audio track the same dials are Auxiliary Send dials.

The other option is to use the Subgroups in the bottom right corner (15 of these available) but this can be more complicated depending on the sound card configuration.
I happen to use that area for multiple outputs on my sound card sometimes as it can be used for either that or combining SubGroups., so AUX is easiest and was designed for this task.

This is correct. Another related application of a buss is to set one fader on a mixing board or console to affect multiple tracks (example: the entire drum kit).

An audio buss is an electrical conduit that accepts incoming signals from multiple sources. Such as controlled by the master/main fader of a console/mixer being fed by signal from several channel strips. In RB and other DAWs we are taking about a virtual/software buss behaving in the same/similar manner as a hardware/wired device. This BUSS basically sums together the incoming signals from multiple channels into what you are hearing; a stereo, left and right or mono output. Because Busses are so handy at summing input signals to something we can use we use them for a bunch of other purposes also. An AUX Buss or FX Buss is intended just for those other purposes. For example; I can put a Reverb PlugIn on an FX buss, then route/send 5 - 6 vocals channels/tracks all to that one FX Buss for the same reverb effect on all 5 - 6 vocal tracks. That FX buss is being sent/routed to my main/master Buss where it is processed to stereo with my other channels/tracks that don't go through the FX buss.
That's about all I have time to explain. But we can do many other things with busses. Keep in mind most of the terminology used for software mixers and DAWs comes from engineering vocabulary of the hardware mixer/console era before software existed. But now, it's virtual.

Great explanation.

It's not always virtual. Pro studios still use mixing boards. I even have a small one at home. But they are going away.

The easiest way, I think, to describe and understand a buss is to simply think of it as just another track. But instead of being side by side with the other tracks it's stacked one step above. In many cases if you use busses, you only have to think of having 3 levels of tracks stacked in a pyramid shape.

You have all your individual tracks at the bottom, you have your sub buss tracks above that and at the top is the main or master buss that sends the total mix out.

So simply put, a buss is a track that accepts the outputs of one or more tracks and sums them all and can be used to apply "like kind" effects. For example, in my mixes, I tend to group all of my guitars into a sub buss to apply the same reverb to them all. I do the same thing with vocals.

Also a buss mix can save you many hours of frustration. Lets say you have your mix perfect.... all the volume envelopes and FX are in place for the instrument mix. It's sounding good. Then you add the vocals in and no matter what you do, the vocals just don't cut through the instruments properly and no amount of compression or boosting gets it done where it sounds good. You come to the realization that the mix is just too loud and needs to be turned down but with the volume envelopes, that's easier said than done. The easy solution is to route all of the tracks you set up for guitars and such, into a new "band" buss where you can then simply pull the fader down to the proper level and now, the vox tracks set properly in the mix. If you have existing busses, you just use their volume fader to set the group level into the master. It's a life saver and has bailed me out more than a few times.

Hope this helps you understand the concept of busses.

"You have all your individual tracks at the bottom, you have your sub buss tracks above that and at the top is the main or master buss that sends the total mix out. "

.. I've always visualized these as top to bottom, not bottom up .. and the end result drops out the bottom. Kinda like an upside-down pyramid.. or like a food processor!

Shove everything in the top funnel and it comes out the bottom all combined.

Course it ain't that simple, but that's the flow I see in my head; funny how some of us think 'up' and some of us 'down' ..
I relate it as 'down the signal chain' so I know why I think like this.

I've also heard the term 'pyramid' mixing so (I think) I see why you may see it the other way.
It's all good, just an observation.

And I see it very much like a 24 channel 8 buss Mackie mixer console connected to a stack of ADAT recorders and some outboard hardware FX patched into the aux sends, sub busses and mix B section all going to a Panasonic DAT recorder via the main output buss of the console.
'cause that's how I used to do it.

Look up the manual for any recent Mackie mixer and look at the signal flow diagram. This will help you understand what a bus is conceptually. Verbal descriptions can only go so far. The various descriptions above are helpful, but getting a graphic depiction might be what you need to grasp the concept fully. Even better would be to experiment with a real hardware mixer and some signals and outboard processing gear.

Here's one that has some onboard effects

http://mackie.com/sites/default/files/PRODUCT%20RESOURCES/MANUALS/Owners_Manuals/ProFX8v2_12v2_16v2_22v2_30v2_OM.pdf