(http://www.vtgrandpa.com/photos/albums/forum_photos/pcdrb_091020.jpg)
Well, I will give you my layman's opinion of what the difference is and that is that The Planning Commission are a group of people that come up with a Town Plan that includes stipulations as to growth in the town and what will be allowed where with rules and guidelines.
The Development Review Board is a group of people that decide when something does not meet certain guidelines, whether it should be allowed or not and what must be done to make it acceptable.
Perhaps one of the best ways would be for you to read the actual minutes from the two different meetings:
Planning Commission Minutes can be found at:
http://www.vtgrandpa.com/fxtown/past-pcminutes-index.html (http://www.vtgrandpa.com/fxtown/past-pcminutes-index.html)
Development Review Board Minutes can be found at:
http://www.vtgrandpa.com/fxtown/past-drbminutes-index.html (http://www.vtgrandpa.com/fxtown/past-drbminutes-index.html)
Keep in mind, this is just my opinion. Skip Taylor at the Town Office can give you a much more intelligent answer.