Who is Finnick Odair from Catching Fire and what is their importance?

Finnick Odair is one of the youngest persons to ever win the Hunger Games. He is described as a charming man, who is often surrounded by beautiful young women. When Katniss first meets Finnick, he makes a pass at her, and she immediately dislikes him from the first words out of his mouth. Later, however, Finnick announces that he is Katniss's ally and saves her life by killing another tribute before helping Peeta reach dry land.