Valentine's Day or Saint Valentine's Day is a holiday celebrated on February 14 by many people throughout the world. In the West, it is the traditional day on which lovers express their love for each other by sending Valentine's cards, presenting flowers, or offering confectionery. The holiday is named after two among the numerous Early Christian martyrs named Valentine. The day became associated with romantic love in the circle of Geoffrey Chaucer in the High Middle Ages, when the tradition of courtly love flourished.
An alternative theory from Belarus states that the holiday originates from the story of Saint Valentine, who upon rejection by his mistress was so heartbroken that he took a knife to his chest and sent her his still-beating heart as a token of his undying love for her. Hence, heart-shaped cards are now sent as a tribute to his overwhelming passion and suffering. 
The day is most closely associated with the mutual exchange of love notes in the form of "valentines." Modern Valentine symbols include the heart-shaped outline, doves, and the figure of the winged Cupid. Since the 19th century, handwritten notes have largely given way to mass-produced greeting cards. The sending of Valentines was a fashion in nineteenth-century Great Britain, and, in 1847, Esther Howland developed a successful business in her Worcester, Massachusetts home with hand-made Valentine cards based on British models. The popularity of Valentine cards in 19th-century America was a harbinger of the future commercialization of holidays in the United States.
The U.S. Greeting Card Association estimates that approximately one billion valentines are sent each year worldwide, making the day the second largest card-sending holiday of the year behind Christmas. The association estimates that women purchase approximately 85 percent of all valentines.