What is the upgrade used for in Pokemon FireRed?

The Up-Grade is used to evolve a Porygon into Porygon2. In FireRed to get a Porygon, you must get 9999 coins at the Rocket Game corner and then exchange them for a Porygon. To get an Up-Grade, beat eight opponents in the Trainer Tower in Seven Island. At the roof-top, talk to the owner who will award you an Up-Grade. Also if you look in Rocket Hideout on island 5 you can find one.
if you give it to your porygon and trade it, it will evolve into a porygon-2.