While people all over the world celebrate St. Valentine’s Day with loving gifts such as roses, chocolates and clever Hallmark cards, some tend to forget that there is a lengthy religious history behind the romantically celebrated day.

As it is commonly known, Valentine's Day or the Feast of St. Valentine is observed on Feb. 14 each year. But who is St. Valentine?

The Catholic Church recognizes at least three different saints named Valentine or Valentinus, all of whom were martyred.

One legend contends that Valentine was a priest who served during the third century in Rome. When Emperor Claudius II decided that single men made better soldiers than those with wives and families, he outlawed marriage for young men. Valentine, realizing the injustice of the decree, defied Claudius and continued to perform marriages for young lovers in secret. When Valentine's actions were discovered, Claudius ordered that he be put to death.

Other stories suggest that Valentine may have been killed for attempting to help Christians escape harsh Roman prisons, where they were often beaten and tortured.

According to one legend, an imprisoned Valentine actually sent the first "valentine" greeting himself after he fell in love with a young girl--possibly his jailor's daughter--who visited him during his confinement. Before his death, it is alleged that he wrote her a letter signed "From your Valentine," an expression that is still in use today.

While it has never been confirmed, history says that Esther A. Howland began selling the first mass-produced valentines in America in the 1840s.

Howland, known as the “Mother of the Valentine,” made elaborate creations with real lace, ribbons and colorful pictures known as "scrap." Today, according to the Greeting Card Association, an estimated 1 billion Valentine’s Day cards are sent each year, making Valentine's Day the second largest card-sending holiday of the year. (An estimated 2.6 billion cards are sent for Christmas.)

Valentine’s Day is also observed in countries such as Canada, Mexico, the United Kingdom, France and Australia to name a few.