That link gives an extremely good explanation of the hisogram feature and how to use it when figuring out your exposure.

IMO, the best part is further down the page when it dispels a common myth about histograms: that they all should resemble a bell curve with the peak (midtones) roughly in the center with tappeing sides (highlights and shadows).

This is not even close to being true. Different lighting situations will yield completely different histograms. Look at the high and low key examples they use.

As a photographer you need to compare the histogram with your perception of the scene (IOW how you're trying to depict it) as well as your light meter readings...