At age 16, Patrick was captured by an Irish raiding party and hauled off to Ireland where for six years he was a shepherd for his captor. He was a pious lad who, according to legend, prayed a hundred times every day and another hundred every night. At some point during his captivity he started to have visions, and eventually had one that told him how to escape.
He made his way safely back home with the help of friendly seamen and soon thereafter went to France to enter a seminary. He was ordained and later was elevated to the rank of Bishop, and, eventually, was commissioned by Pope Celestine I to go to Ireland to convert the Celtic tribes.
His landing in Ireland was inauspicious -- the ship was blown off course (and, according to some accounts, he was shipwrecked) on the coast of Ireland. The local chieftain did not want to be converted, but, when he raised his arm to strike Bishop Patricus, the Chietain's right side was paralyzed (we're slipping into legend here) and he couldn't move until he accepted Christianity.
Patrick stayed in Ireland for more than thirty years, and, by the time of his peaceful his death in Downpatrick in 493, he and his followers had converted all of the tribes. The legendary 365 churches he founded have not all been located, but more than ninety of them are known and still have active congregations. Every Irish town has a St. Patrick legend, and he apparently slept in every Inn in the land -- even the ones that were built long after he died.
St. Patrick's Day, as celebrated in Ireland, is not the boisterous affair that it is in the Boston, New York, Chicago, and other US cities. Religious processions and observances occupy the morning and family gatherings the afternoon, after the 12 O'clock Mass. The men (and, in the bigger cities, the women too) adjourn to the pubs in the evening, but green beer is only served to American tourists. It's considered bad form to get drunk on St. Patrick's Day, but the Irish have never worried very much about good form anyway.
In recent years, the city of Dublin has realized that there is a lot of American tourist money to be made, and so now there is a big American style celebration, with a parade and other touristy stuff. Naturally, the "official" St Patrick's Festival has an Internet web site (see below).
For facts and legends, visit the following Internet sites:
http://www.newadvent.org/cathen/11554a.htm The Catholic Encyclopedia Biography
http://www.geocities.com/CapitolHill/7652/patrick.htm More Facts and legends
http://goireland.miningco.com/travel/goireland/library/weekly/aa031097.htm an About.com page about the real St. Patrick, with links to other St. Patrick Internet items.
For Information on the "official" St. Patrick's Festival in Dublin (pictures, music, movies, travel info!!!)
http://www.stpatricksday.ie/ Plan to go next year!
PS -- Shamrocks: St. Patrick is said to have used the common shamrock to explain the Christian Trinity to the heathen Kelts.
Snakes: there are, we are told, no snakes in Ireland because St. Patrick drove them out. Several examples of his preaching and prayers refer to the devil as a snake and his followers may well have made Irish snakes extinct in an excess of religious fervor.
Leprechauns, banshees, and other critters: pagan stuff. Nothing to do with the Saint.
Irish (Kelly) green: Go to Ireland. It really is that lush vegetal color due to the almost constant rain and mist.