Neoptolemos (also known as Pyrrhos) was the son of the Greek hero Achilles. After the death of his father, the other besiegers of Troy were told by the Gods that they could only win the war with Pyrrhos and they ordered him in. Oddyseus gave him a nice shiny armor and Neoptolemos helped win the war which involved some big wooden horse-thingy. While he was at it, he killed Priamos (king of Troy), the son of Hektor (son of Priamos) and took Hektors wife, Andromache, as his. After the Greek won they named Pyrrhos Neoptolemos (Neoptolemos means new war).
Later married the daughter of Menelaos (brother of the king of Greece), Hermione, and was killed by her previous lover.
For all you "Troy" lovers, the movie was totally and utterly wrong about just about everything. Achilles never entered Troy, Neoptolemos was in the horse.