Should you "normalize" when mastering?

depends on the sound. Generally I am in the anti-normalise camp. If you mix and master your track well with compression and limiting there should be no need to normalise.

JG

Normalising simply looks at the highest peak and add or subtracts volume to the file so that this highest peak is at 0 dB. So if your highest peak is at +3 dB, Normalise will subtract 3 dB from the whole song. If the peak value is very low, the whole song will be massively raised, also raising artefacts and noise.
However, of your peaks are around -6 dB (rule of thumb), normalising will do no audible damage, but just add 6 dB to the whole song.
It doesn't do anything else but automatically raising (or lowering) the overall volume. But, if you see in your meters that your highest peak has been -2.8 dB, you can simply up the master fader from 0 to 2.8. It's the exact same result as when you'ld normalise.
There appears to be an anti-normalise camp, but I am not one of them. You should mix as decent levels though, not that you have to add another 10-20 dB by raising a fader (or normalising).

regards, Erik.