what is each bin or pixel in the hist2 program telling me?

Hi, I'm having trouble understanding what the hist2 program is telling me. Descriptions that I've found tell me that it is a 2 dimensional histogram, or the joint histogram of X and Y, but I'm confused as to what each color pixel represents. For example, if the x-axis represents a rats position on a linear track and the y-axis represents the envelope amplitude of a signal (and let's say its a 30 x 30), what does each color bin or pixel represent? (This is a recording from a rat where he ran back and forth on a track ~ 50 times). The color bar goes from 0-.2, with .2 being dark red. Some bins on the histogram are dark red while others are not. Does each pixel represent probability, such that a dark red pixel of .2 represents the probability (20%) that the envelope amplitude of a signal will be X given that the rat is on X position on the maze? This makes some sense to me, but any further interpretation would help. Thanks a lot.

[Sean de Wolski]

What is hist2?