Valentine was a Roman nobleman who gave his home to be used for Christian marriages. Valentinus, as he was called in the ancient language, died for the Faith on February 14, and since the Middle Ages has been associated with love.
The day was first associated with romantic love in Geoffrey Chaucer’s works in the High Middle Ages, when the the ideal of courtly love flourished. This was especially true in 18th-century England.
Christians ought to love as Jesus loved: complete self-giving. Remember to love well.