Tom Buchanan is a multimillionaire heir of the East Coast. It is implied that his inherited fortune comes from the industrial ravages of the robber barons of the Gilded Age. Being raised in a wealthy environment, Tom Buchanan has had a Classic, extensive education in Yale University, one of Ivy League’s best. Thus, he has bee taught taste and manners, although it is clear that he lacks true intelligence.
Jay Gatsby on the other hand, is a new millionaire; in those times these were called “new money”. He has acquired his wealth by bootlegging and smuggling alcohol into the United States during the Prohibition. Because he was born into a family of very poor extraction, he lacks the taste and manners of Tom Buchanan, although he compensates with his intelligence and resourcefulness.
Tom Buchanan, learning that Gatsby is having an affair with his wife Daisy, confronts him about this and about the illegal origins of his wealth.