East and West Egg are symbols of class. Gatsby and Nick live on West Egg. Daisy and Tom live on East Egg. Gatsby can only gaze at the "green light" of East Egg from his house. Gatsby is "nouveau riche" (newly rich), but Daisy has "old money" and that is the bridge that Gatsby wants to cross, but cannot. Daisy was born into money, he was not.
The "Valley of Ashes", watched over by "the eyes of Dr. Eckleberg" is a symbol of class. On one side are the rich, on the other lower class people such as Myrtle, Tom's mystress.
Gatsby's parties are a symbol of class. He gives these lavish parties to prove that he is worthy of Daisy, that he is on the same level, but most of the people that come are suck-ups that don't even know Gatsby. His parties are a hollow attempt to prove he is in the same class, which he is not.
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