Nick Carraway is the narrator of the novel. He's a young man from Minnesota that went to Yale and World War I. In the beginning of the novel, he goes to New York City to learn the bond business. He moves to the West Egg, next door to Jay Gatsby. Later on in the book, Nick helps Gatsby rekindle a romance with Nick's cousin, Daisy.
Jay Gatsby is a wealthy young man that lives in a great mansion in the West Egg, next to Nick. He's famous for throwing extravagant parties every Saturday night, but nobody really knows much about him or his history. Nick learns that Gatsby fell in love with Daisy while training to be an officer in Louiseville and that he made money through criminal activity.
Tom Buchanan is Daisy's wealthy husband. He used to be a member of one of Nick's clubs at Yale. He has a strong and well built appearance. He's an arrogant, racist, sexist, and inconsiderate person. He's been cheating on Daisy with Myrtle Wilson.
(information from The Great Gatsby by F. Scott Fitzgerald)