the tune is many factors in how your truck operates.,
the air/fue ratiol, and spark timing. shift points, rev limiter, how soon to shift, shift pressure..
the way I explain it is. ford has tuned the truck your all the uses and needs of the customer
. a programmer or tuner is a device that can adjust the settings or tune of the truck yup be more specific to the customers needs. rather then everyones.
I have a super chips programmer from my last truck. there is different settings I can choose from.
87 mileage- optimized for 87 octane. geared more for fuel economy. not allowed to tow with it.
87 performance-.optimized for 87 octane, performance. firmer shifts. won't shift a soon as mileage. no towing above 2000 lbs
91 performance - optimized for 91 octane, performance, tighter advanced timing, shifting, firmness increased over mileage tube, same as 87 performance tune. no towing above 2000lbs
87 Towing - optimized for 87 octane. modified shift pattern and shift pressures., best towing large loads.
so you see it just makes the vehicle more specific for the drivers needs. pending on your needs at the time you can change it, and revert back to stock when truck has to go into ford for service.