What is the function of the Send and the Output in the audio track strip?  If I have a bus with a cool effect and I want multiple tracks to use that effect; do I route the signal from the Send and/or Output in the audio track strip?

It depends. In a virtual mixer like SONAR's, there is no functional difference between a Send and the track's main Output. They're the same, except that you can have multiple Sends. Think of the Output as the default Send that's always there. If you want to use that bus effect in parallel, then a Send is what you want to use.

Good onya Bit!

Thanks!  I'm a musician/composer/arranger/software developer.  It's easy for me to get wrap around the axle with stuff like this.

As that wise sage Wachowski said "there is no spoon". It's all virtual and only exists in your mind.
 
"Wrapped around the axle" - that's good, I'm going to add that to my personal lexicon.