FFT and the values ​​of the array

[iacoposk8]

In this example:
http://mohayonao.github.com/timbre/documents/fft.html

in the function WaveViewer.animate, there is the following code:

for (i = step, imax = wave.length; i < imax; i += step) {
y = (wave[i] - min) / (max - min);
context.lineTo(i * dx, height - (height * y));
}

wave in the array (I think) there is a list of volumes achieved by the different frequencies at that time from the audio file

1. these volumes in which units are? decibels?
2. for example, in the array, the position 35 corresponds to that frequency?
   thanks :)