Normalize is a digital process where the audio file is scanned and the peak signal level is determined. The overall volume level of the file is then raised such that the peak signal is just below digital full signal. If done to several tracks the peak levels will sound the same, but the average volume of any given track may still be higher or lower than another track.
Don't normalize if any other digital manipulation is to follow.
Don't normalize if any other digital manipulation is to follow.