What does helen symbolize in the Iliad? Is she a person and why would they fight over someone they don't know?

In the Iliad, Helen is a woman of immense beauty for whom thousands of men are willing to fight and die. But is she really a woman? Would 50,000 men really be willing to leave their homes for 10 years just to fight for one woman whom they do not personally know? Most literary scholars believe that this is highly unlikely. So, if there wasn't a woman named Helen, and she is just a symbol, what does she represent? The Iliad is full of clues as to what objects and concepts that Helen represents. I have to write a persuasive essay to convince the teacher of three objects/concepts that I believe the character Helen symbolizes in the Greek epic but I don't understand what she is, what is Helen?!