At the beginning of the play, the characters keep referencing a check that is supposed to be arriving the next day. The audience learns that this check is a life insurance check, and it's coming because Mama recently lost her husband, Walter Sr. The check is worth $10,000, quite a large sum for this poor family that lives on Chicago's Southside.
This check is the center and symbol for each of the family members' dreams. For Mama, she dreams of a house where her family can grow and flourish. Currently, she, her daughter Beneatha, her son Walter, her daughter-in-law Ruth, and their son Travis all live together in a very small apartment. Because of the cramped living conditions and because of their poverty, Mama and the audience see the deterioration of Walter and Ruth's marriage, and Mama wants more for them and for her grandson.
For Walter, the check represents a chance to be a man, the leader of the family. Walter wants to use the money as a downpayment on a liquor store, which he thinks will make him big money. For Walter, money means power and respect. Currently, he is a chauffeur for a wealthy white family, and Walter idolizes that family because he thinks they "have it all." So the money would mean the American Dream for Walter.
For Beneatha, the money would mean a college education and a chance to create an identity for herself. Currently Beneatha is the only adult in the household who is not working to support the family. She is trying to attend medical school, but really, that is just one step in trying to find out who she is supposed to be--her identity.
For Ruth, that money would just mean happiness for her family that seems to be falling apart. While Ruth does not have specific plans for the money like the other main characters, she thinks that the money can make the other three happy in their endeavors. That dream is complicated, however, when the audience discovers in Act I, scene II, that Ruth is pregnant. Because of the family's poverty, Ruth feels she must give up the baby in order to keep the family together. That $10,000 could mean the opportunity to keep the baby.