Here is from Google
The History of Valentine's Day
Every February, across the country, candy, flowers, and gifts are exchanged between loved ones, all in the name of St. Valentine.But who is this mysterious saint and why do we celebrate this holiday?
Valentine's Day is on February 14. It is the traditional day on which lovers express their love for each other; sending Valentine's cards, candy, or donations to charities, often anonymously. It is very common to present flowers on
Valentine's Day. The holiday is named after two men, both Christian martyrs named
Valentine. The day became associated with romantic love in the High Middle Ages, when the tradition of courtly love flourished.
http://en.wikipedia.org/wiki/Valentine's_Day