Welcome to the forum, by the way.
I think it might be worth your running through the tutorials that come with Sonar. There is a lot to learn, I'm afraid. I will try to explain briefly, but I would also recommend watching the Videos on the Cakewalk site, and probably buying the Groove 3 or SWA X2 explained videos. I think Karl's (fastbikerboy on here) videos would help you a lot.
Audio from a track in Sonar has to be routed out somehow. In the console view (the part of Sonar that looks like a mixing desk) the signal (or sound) runs from top to bottom, just like a real desk, from the input to the output. You can choose to "send" some of this signal elsewhere, e.g. to be processed by a reverb, whilst the rest of the signal continues to the channel's outputs. That is what a send is. It determines how much of the signal is sent elsewhere.
The fader is the slider at the bottom of the channel that increases or decreases gain (or volume) of the channel.
I have grossly oversimplified this, not to mention explained it badly, so I strongly suggest watching the above mentioned videos, and reading up on recording and mixing audio.
I can recommend some reading on the topic, if you want, but am off to bed now.
Good luck with your audio journey.