Quick Dialer is a simple app that aids you if you happen to live in a part of the country that has area code overlays.
With overlays, there are two different area codes for one region, so you have to enter in the area code every time you dial the phone - so you always have to enter in all 10 digits (11, including the 1).
Quick dialer allows you to enter in the default area code for your area, and will automatically append it to the number for you, so you can go back to dialing just he seven numbers!
Just enter in the number, such as 867-5309 (and for those of you younger then 30, that was the number for Jenny in a very famous song sung by Tommy Tutone) press the dial button, and wolla - your phone dials with the area code!