The Aenied is an epic poem written by Virgil in the 1st century BC. It's hero is Aeneas, a Trojan who travels from Troy to Italy to eventually found Rome. Some argue that The Aeneid is Virgil's answer to Homer's Odyssey and Iliad, combining two genres of the day - travel and war - into one poem. Take that, Homer!
No civilization is without a bit of revisionist history: so it was that Virgil picked up the story of Aeneas, which was already floating around at the time, and forged an epic founding myth for Rome. And The Aeneid fit the bill, as it linked Rome with the legends of ancient Troy, glorified stodgy Roman values, and legitimized its emperors as descendants of the heroes and gods of the past. George Washington probably didn't chop down a cherry tree, but it's a fun legend to tell the kids.