If something is a cakewalk, it is very easy to do, or a win that takes almost no effort. “The test was a cakewalk.” “They won in a cakewalk.” It is informal. The name is cake + walk, but the meaning is not about walking on cake. It comes from an African-American dance that grew after the American Civil War (and had an earlier life on plantations): a proud, high-stepping dance that copied, and made fun of, fancy ballroom dancing. The best dancers often received cake as a prize. Slaveowners treated the contests as entertainment, and the habit of offering cake may start there. Because taking the prize could look easy and showy, cakewalk later came to mean “something easy”. The dance itself sat inside a cruel history, so the bright modern meaning sits on top of something much harder. In ordinary talk now, cakewalk almost always means “easy”; the dance sense lives on mainly in history and music writing.