Saint Patrick's Day commemorates Saint Patrick and Irish culture. It is celebrated on March 17th each year. People wear green clothing and shamrocks are used to symbolize the Holy Trinity of Father, Son, and Holy Spirit. If someone is not wearing green, they may be pinched. Common celebrations include parades, eating Irish foods like corned beef and cabbage, and drinking Guinness. Saint Patrick was born in Britain and captured by Irish pirates as a slave in Ireland at age 16, where he learned Gaelic and helped spread Christianity before returning to found churches and monasteries.