At age of 14 he was taken off by raiders to Ireland as a slave. In his captivity he turned to God. By his early 20's he had fled his captors and returned home with a new passion and a desire to become a priest. His preaching of the faith resulted in many converts. Quite often he is shown holding a three leafed clover which is symbolic of the trinity: Father, Son, and Holy Spirit.
Today is a celebratory day for many Irish people. Although the focus tends to be on green beer and shamrocks and leprechauns... The origins of today began as one man serving and listening to God's call to convert the Irish back to their faith.
Happy St. Patrick's Day!