In the 5th century when St. Patrick came to Ireland to convert the Irish to Christianity, the information could only be spread across the realm from one storyteller, or seanchaí (pronounced shan-a-key) to another seanchaí.
With this in mind, St. Patrick used to the Shamrock to explain the concept of the holy trinity - that God was composed of three entities - the Father, the Son and the Holy Spirit - yet each entity was part of the other, just like the shamrock has three leaves, but each share a single stem.
It is for this reason that the Shamrock is worn on the St. Patrick's day and all other special occasions to celebrate his work and to bring 'a bit o'luck' to the Irish, and all their children, wherever they may be.
The four-leaf clover is an uncommon variation of the common, three-leaved clover. According to tradition, such leaves bring good luck to their finders, especially if found accidentally. In addition, each leaf is believed to represent something: the first is for faith, the second is for hope, the third is for love, and the fourth is for luck.
It has been estimated that there are approximately 10,000 three-leaf clovers for every four-leaf clover; even so, this probability has not deterred collectors who have reached records as high as 160,000 four-leaf clovers.