One of the major themes of the book, Lord of the Flies,is the tension in all of us between order and chaos, or savagery and civilization. The protagonist, Ralph represents the former and Jack, the antagonist, represent the latter. Golding is suggesting that we all have elements of both in our hearts.
With that backdrop, the conch is an important symbol in the story for two reasons. First, the conch is used to bring people together. It is, therefore, a force for order and unity. It represents civilization and order. When the conch is broken, this is a very symbolic moment, because this suggests that order is now no longer what governs the boys. Even a look at the novel will show that after the conch is broken, things get considerably worse.