The A-Wing was designed by Walex Blissex, and based on the shape of his hand. It was named A-Wing because Blissex didn't know that many letters, and X and Y were already taken. The ship was designed for speed, but did also have some weaponry. They were outfitted with standard lasers, concussion missiles, and hyperdrive.
While the primary function of A-Wings was to engage with TIE Interceptors and other small craft, their small size and speed allowed them to engage much larger crafts. In a one-on-one fight, and A-wing could take down a Star Destroyer- though this was incredibly risky to the pilot. During the Battle of Endor, Arvel Crynyd flew his A-Wing directly into the bridge of the Super Star Destroyer Executor, causing it to crash into the Death Star.