Computer relearning

I recently posted a thread regarding reduced MPG on my '94 3.0. One of the suggestions was to disconnect the battery, wait 30 mins and then cycle the key on and off a few times and take a drive to allow the computer to relearn. Now, my successful days as a mechanic ended when cars got more complicated than my '49 Chev. So tell me a little about how this "relearning" procedure could effect my gas mileage. Or, give me a link to a site that could explain this to me. I will be doing this today. Thanks