The parties represent many things, actually. First, they are a ostentatious show of wealth, intended to illustrate Gatsby's power and prestige to Daisy. The reality of the parties versus the fantasy that they portray is another aspect. The reality of the parties is that they are not true parties, at all in fact, since Gatsby does not know half of the people there, nor did he actually invite them. People do not come there to visit but rather to have risque liaisons and to engage in semi-legal activities. And, finally, the represent America in all its young glory...partying without a cause....with no real governance, rules, or direction: a young country drunk on itself.