Root x Mean ^2 (root mean squared). It's the average level. Audition's meters are peak meters. Normal analog meters are RMS meters and their behavior most closely resembles human hearing of levels. There are a few manufacturers that make meters specifically for measuring percieved loudness, but they're very expensive and not *much* different than RMS.
The scale (digital full-scale or dBFS) ranges up to 0dB. For a 16-bit file, the range is -96dB to 0 dB with 0 being the loudest and -96dB being the softest. 24-bit ranges from -144dB to 0 dB. Peaks can go all the way up to, but not exceed 0db. The closer to 0, the louder the file, but you would never have a file that is 0dB RMS, as it wouldn't sound like anything. Most commercial CDs fall between -10 and -15dB RMS. Mastering engineers use compression and brickwall limiting to raise the RMS level without allowing peaks to exceed 0dB.