The Claddagh is an Irish symbol. Expanding on the writeup above, Richard Joyce was said to have been engaged when he was captured. He spent many years in slavery thinking about the girl he loved. He stole gold from his master in tiny pieces, eventually getting enough to make a ring. The first claddagh ring. When he was freed he returned to the village of Claddagh with the ring to find that his love had not married, but instead had been faithful to him despite everyone telling her he was dead. The Claddagh ring became a symbol of love, loyalty and friendship.
The Claddagh has also been said to represent other things. The right hand represents Dagda, the celtic father of the gods. The left hand represents Danu, the mother of the gods. The crown represents Beathauile. "Beathauile does not appear to be a person or a god but appears to represent all of life. Gaelic-English dioctionaries indicate that beatha translates to the word life and uile to the word whole or all."* The heart represents the hearts of all mankind.
Another interpretation of the Claddagh symbol is that it represents the holy trinity - a symbol very important in Irish culture - and is related to the Shamrock. The crown represents the Father, the left hand the son, and the right hand the Holy Ghost. They surround the heart in the middle which represents mankind.
*http://qsilver.queensu.ca/~fletchra/Claddagh/ | 
