I believe I understand now - you get both a processed and unprocessed signal when you route to a send.  I set up a quick test with a simple audio loop.  I added a send to the bus with an effect that was hard to miss.  When I routed the track itself to "none" i only heard the processed audio.  When I set the send output to none, I heard only unprocessed audio.  Both set to master I heard a mix. 
 
A send would then only be useful, then, as Bitflipper said, when multiple tracks use the same effect.  Got it.
 
Thank you all for your help.  

bitflipper
Next-most frequent application is parallel compression. You might, for example, send more of a lead vocal's double to the compressor than the primary lead vocal track.
 
Parallel distortion is another common scenario. I'll use send levels to send some kick drum to a distortion plugin, send a higher level to it from snare and toms, and usually none from the overheads.

To add to this, I use sends for all kinds of parallel processing. For example using effects on bass will often thin the sound, so you send the main bass track to the master, and use a send to go through the effect. That way you can add wah, distortion, envelope-controlled filtering, and the like without affecting the bass's low end.

I always thought a send was kinda like the effects loop on a guitar amp.  In other words, it lets you tap into the signal chain with effects at a different point than just putting the effects plugins in the bin.  When you put the plugins in the bin, they come "before" the audio, where a send is basically coming AFTER the audio (i.e., the effects loop comparison).  Is that incorrect?

Husker - You may have received too much information in this thread. It's all good, and eventually you'll want to know all that stuff, but your picture above is perfect, and it's all you need to know about sends for now. Using the setup in your picture, your sends pick off some of the signal on each track and send it over to the reverb bus, which feeds reverb only -- in the amount you choose using your sends -- into your master bus and into your mix. If you didn't use sends you'd have to add a reverb effect in the FX bin of each track where you wanted reverb. All kinds of problems could arise from that, from exceeding the limits of your computer to having your mix sound as if every musician were playing in a different city.
 
Later you can add more sends and more different effects, but some of the best records ever made had one reverb send going to one echo chamber, period.

Hi,
Your template idea sounds really nice. I'd like to try it! Still a noob trying to figure out a good go-to way of doing things.
With your drums, can you use just one instance of say, addictive drums, and route the individual parts of.the kit to separate tracks? Or do you have to setup many instances of a drums intrument?

I have more questions, but I'll leave it at that for.now, lol.
Thanks

BassRocket

With your drums, can you use just one instance of say, addictive drums, and route the individual parts of.the kit to separate tracks?

Yes, but it has nothing to do with this thread. Read this blog. It was written for X3 but works for newer versions too.

Thanks Scook!

This post sure opened a large can of good ideas folks are posting 😊.

Another useful application for sends is setting up alternative headphone mixes.
I always have a send on each sub-buss - drums, keys, guitars, vocals etc, routed to a Phones bus.
This bus doesn't go to the master bus but to a spare pair of interface outputs, in turn routed to my headphone amp.
It's easy to vary the amount of each bus in the headphones by varying the send level.

Bristol_Jonesey
Another useful application for sends is setting up alternative headphone mixes.
I always have a send on each sub-buss - drums, keys, guitars, vocals etc, routed to a Phones bus.
This bus doesn't go to the master bus but to a spare pair of interface outputs, in turn routed to my headphone amp.
It's easy to vary the amount of each bus in the headphones by varying the send level.

I just put one send on the master bus to go to the headphones - unless you want a phones mix that is different than your master mix, that's seems like doing it the hard way.