Clean Monday is a special holiday celebrated in Greece (and other countries with Greek Orthodox Christian populations) that marks the start of Lent, a time when people give up things they like (such as sweets or TV) and focus on being good and doing good things. On Clean Monday, people go to church and feast on special foods like seafood, vegetables, and a special type of bread called "lagana." They also often participate in special activities like flying kites or playing games. The holiday is called Clean Monday because people traditionally clean their homes and start fresh for the Lenten season. Overall, it's a time for reflecting, cleansing, and making positive changes in your life.