I dislike posting up "official summaries", but here's one anyway (I really couldn't do it justice with my own attempts).
FEBRUARY 1945 Even as victory in Europe was finally within reach, the war in the Pacific raged on. One of the most crucial and bloodiest battles of the war was the struggle for the island of Iwo Jima, which culminated with what would become one of the most iconic images in history: five Marines and a Navy corpsman raising the American flag on Mount Suribachi. The inspiring photo capturing that moment became a symbol of victory to a nation that had grown weary of war and made instant heroes of the six American soldiers at the base of the flag, some of whom would die soon after, never knowing that they had been immortalized. But the surviving flag raisers had no interest in being held up as symbols and did not consider themselves heroes; they wanted only to stay on the front with their brothers in arms who were fighting and dying without fanfare or glory. ‘Flags of Our Fathers’ is based on the bestselling book by James Bradley with Ron Powers, which chronicled the battle of Iwo Jima and the fates of the flag raisers and some of their brothers in Easy Company.
I recommend you visit http://www.flagsofourfathers.net/ (a wonderful fansite) and the official movie website for more information.
Think of it as a clique you can join online to show you like a certain subject (places, people, things...). If you're still going "huh?", here's a better definition by TFL.
A fanlisting is simply an online listing of fans of a subject, such as a TV show, actor, or musician, that is created by an individual and open for fans from around the world to join. There are no costs, and the only requirements to join a fanlisting are your name and country. Fanlistings do not have to be large sites (although some are) - they are just a place where you can have your name listed along with other fans of the same subject.
There are no costs or harmful side effects, so feel free to join. :D