Aurebesh was a writing system used to transcribe Galactic Basic Standard, one of the most used languages in the galaxy. In the Outer Rim Territories, Aurebesh was sometimes used alongside Outer Rim Basic, another alphabet.
During the Clone Wars, some clone troopers customized their armor with Aurebesh phrases. The back of clone trooper Ponds’helmet had the phrase «Some guys have all the luck» written in Aurebesh. Others got Aurebesh tattoos. ClonemedicKix, had the phrase «A good droid is a dead one» tattooed on the side of his head, although the tattoo was eventually covered up when he grew his hair out late in the war, while trooper Sketch had his initial, Senth, tattooed on his forehead. In the same vein, some Low Altitude Assault Transports were personalized with Aurebesh, such as the Spaceward Ho! and Lucky Lekku, both of which bore their names, and the Crumb Bomber, which bore the phrase «LAUGH THIS OFF.» The patrol transports used on Coruscant were emblazoned with the word «POLICE.»
If the Star Wars galaxy uses the Aurebesh writing system for everything, why do we see starfighters with names like X-Wing and Y-Wing? That’s because while Aurebesh is the most common, it isn’t the only writing system in the galaxy. The High Galactic alphabet is identical to the real-world English alphabet. So we can assume that the Incom Corporation named the X-Wing for its similarities with the letter X, just like in the real world.