The Sienar Fleet Systems TIE/ln starfighter or TIE/line, simply known as the TIE Fighter, was the standard Imperial starfighter seen in massive numbers throughout most of the Galactic Civil War and onward. It was designed in-universe by the Empire's weapon designer Raith Sienar, famous for creating many other Imperial weaponry.
This one-man small attack craft was highly maneuverable and fast, but lacked deflector shields, so it was usually deployed in vast numbers. It was armed with two laser cannons. The craft also didn't have any hyperdrive, making it dependant on larger vessels for hyperspace travel.
The name TIE Fighter stands for Twin Ion Engine Fighter.