This dummy needs help understanding Sonar's meters....

I would assume that everything referred to as dB in the digital world is just an abbreviation for dBFS.  I also think that if this topic is expounded upon in detail, we will have a general increase in knowledge for gain staging analog and digital components, but I also think the differences can't really be heard until they add up to an overly saturated mix or something odd happening that's hard to fix.  I think we should talk about it.  

Dreamer
What are they? My understanding is that dB is used for analog audio and dBFS is used in digital hardware/software audio. Why are Sonar meters described as VU, (an anolog standard)? Are they VU meters with three different flavors, (rms, peak and peak+rms)? Why aren't they dBFS level meters? Every time there's a subject on volume here in this forum referring to Sonar, I keep seeing descriptions in dB. Even in Sonar's help program volume is described in dB. I assumed all DAW programs are digital not analog. So again I ask, (I am very confused), what are they? There is nothing I could find anywhere as to what they are. Isn't the level output reading supposed to be dBFS? Even the measurement range selection for the meters is in dB. Please excuse my dumminess...I'm just so confused.

Download a third party Level Meter Plugin and run some test compared to Sonar meters, and you can probably figure out yourself what you are actually seeing in Sonar. Think there are some decent free ones out there, if I am not mistaken (dBFS and VU types).
For my final mix I always use third party Level Meters, as well as for my gain staging and especially for Mastering. Yes Sonar could probably have more accurate level metering, although to be fair, IMHO,I haven't used a DAW yet that has accurate level meters, and I use a few.
Just my 2 cents.
 

Dreamer
What are they? My understanding is that dB is used for analog audio and dBFS is used in digital hardware/software audio. Why are Sonar meters described as VU, (an anolog standard)? Are they VU meters with three different flavors, (rms, peak and peak+rms)? Why aren't they dBFS level meters? Every time there's a subject on volume here in this forum referring to Sonar, I keep seeing descriptions in dB. Even in Sonar's help program volume is described in dB. I assumed all DAW programs are digital not analog. So again I ask, (I am very confused), what are they? There is nothing I could find anywhere as to what they are. Isn't the level output reading supposed to be dBFS? Even the measurement range selection for the meters is in dB. Please excuse my dumminess...I'm just so confused.

Ok... (cracks knuckles) let's take a shot:
Firstly, this article in the  TapeOp website http://tapeop.com/tutorials/54/meters/  has excellent perspective about the  behavior of VU meters and the need for other types of metering. 
 
Backward compatibility is reasonably possible to emulate, and there are a variety of plugins that attempt to mimic the mechanical ballistics and behavior of VU meters in the software.  As noted in the article, there are assumptions about the true peaks that are inherent in the mechanical ballistics that make it unsuitable for really keeping the reins on your musical compositions. 
 
In every DAW the meters are a dBFS scale.  The movement of the meters' lights/LED's, or green/yellow/red area fills can be coded to be true peak, RMS, temporary peak indicating, long-term integration, the combo plate with fries, or anything else the coders can make for you.  It has been a long time since I've used Sonar 8.5, so I don't recall how many metering behaviors were available in that release. 
 
Once your tracks are summed to the master output, then you're getting to the point where the calibration of the dBFS to the actual electrical levels of the D/A converter and the input sensitivity of the amp/speakers, and the dB SPL level in the air at your listening position begin to matter a great deal. 
 
In my studio, I've calibrated a -18dBFS level mono 1kHz sine wave output to be 80dB SPL at my listening position. That -18dBFS was calibrated on the input to be +4dBu.  In between, I can have a party with levels all over the place. 
 
I hope this helps you on your way.  Check out my articles for more detail.

My 0.02c. Peaks up to -0.1 are OK at mastering stage. Best to leave a few dB if sending off to mastering.
I've found RMS from -12 to -14 dBFS gives a reasonably loud mix without restarting the loudness wars!
I think there are different ways of measuring RMS (e.g. different K-metering standards, LKRS/LUFS) that take into account human hearing. I believe Sonar uses standard unweighted RMS.
 
dB is a relative measure. It compares the RMS of two signals. dBFS compares to full-scale. Two signals can differ by 5dB (say), or a signal can have a level of -3dBFS. See here for a little more info.
 
Cheers, Peter.

Dreamer
Thanks John. Although I know what the track meters are I'm not sure of what you mean by "track fader or gain". Is that the volume and trim parameter?

Yes. The trim is now called gain. Fader is the control on the track volume control.