In "Lord of the Flies," when the conch is blown, the children hear it, and they go to where it is. The conch, then is a call for all to assemble, and it represents the order of the assembled children and well-behaved, respectful communication. It is thus real and symbolic at the same time. When you hear the conch, you come together as a group, and then, once assembled, if you hold the conch, you have the right to speak. The conch represents the right to assemble and freedom of speech.
Perhaps the earliest example of such an idea is the ancient Hebrew's use of a ram's horn, known as the Shofar. The Shofar was, and still is, used to announce the new year, Rosh Hashanah, and to call all Jews to the temple. It is also used to mark the end of Yom Kippur. Ironically, in terms of "Lord of the Flies," the blast of the Shofar was also used to amass worriers and to announce an advance on the enemy.