Okay, lemme open it up. I've looked at those kinda techie articles about dB, and they never really helped me record better. So, here's my understanding:
1 Zero's the ceiling. When the meter indicates that the signal has gone above zero, it means you've got distortion if you're recording digitally.
2 Everything goes down from zero. -1 dB, -2 dB, -3 dB, and so on. One dB is the smallest change in loudness easily perceptible to most listeners. I can hear smaller differences than that sometimes, in relation to other tracks in the mix.
3 If you go down low enough, the signal gets so quiet that it disappears into and gets swallowed up by the noise floor, which is the unavoidable noise generated by the electronics of your gear. The idea is to get as low a noise floor as possible, so that it isn't very audible in your recordings.
4 Conventional wisdom says to record pretty close to zero, without clipping of course. But if you're recording at 24-bit or above, then it isn't as important. In fact, Sonusman recently talked about not being worried at all about hitting as close to zero as he can.
Okay, anything wrong with that?
Next question: anything else important I should know about dB that will actually help me get better recordings or mixes?