"Instructions: Socrates believed that the “ideal city” should be comprised of three classes. What are these classes, and what does he believe are their proper roles?”
First you have the Auxillaries. these are the army. Their purpose in the State is to protect justice and follow/enforce the laws set out by their leaders.
Second you have the Guardians. These are the rulers of the State, those that are the best of the best and are therefore rewarded.
Lastly you have the Trader. This term refers to your everyday man and woman who are the cobblers, husbanders, shepherds, and so on.