Saint Valentine's Day is a holiday celebrated on February 14th every year and is a tradition dating back to the early middle ages.
 In North America and Europe, it is the traditional day on which lovers express their love for each other by sending Valentine's cards, presenting flowers, or offering confectionery.

Many people however follow these traditions without question, although others do wonder about the history of Valentines Day.
As you may suspect the day is named after a Saint Valentine, however not one but two.

Valentine of Rome, and Valentine of Terni.
These two were both recognized as martyrs by the Church.

They were killed because of their religious beliefs, or rather because they refused to give up on those beliefs.
They were both buried in the early middle ages at different locations on the Via Flaminia, an old Roman Road linking Rome to Rimini in Italy, however some sources also state it was also named the Ravenna road which connected Rome to Ravenna.

One legend of St Valentine of Rome is recorded in the Legenda Aurea which states that Valentine was persecuted as a Christian and interrogated by Roman Emperor Claudius II in person after he was arrested for secretly performing marriage ceremonies for young men. Prior to this the Emperor had passed a law that forbid marriage, believing that married men did not make good soldiers since they would always be thinking of their own family back home while they were away at war, or on guard duties.

Claudius was impressed by Valentine and had a discussion with him, attempting to get him to convert to Roman paganism in order to save his life, however Valentine refused and tried to convert Claudius to Christianity instead.
Because of this, he was executed, and then buried on the Via Flaminia road.

Valentine of Terni became bishop of Interamna (modern Terni) around circa 197 and is said to have been killed during the persecution of Emperor Aurelian. He is also buried on the Via Flaminia, but in a different location than Valentine of Rome.

Interestingly these two Saints were also buried on the exact same day, February 14th, although in different years and locations.
Over the years after their deaths more and more churches begin to officially recognize them for who they were, and what they did.

Now, what does this have to do with love - which Valentine's Day is so known for?
Absolutely nothing.

The first recorded association of Valentine's Day with romantic love is in Parlement of Foules, a poem written by Geoffrey Chaucer in the late fourteenth centaury to honor the first anniversary of the engagement of King Richard II of England to Anne of Bohemia.

For this was on seynt Volantynys day Whan euery bryd comyth there to chese [choose] his make [mate].

Another verse that relates to romantic love during Valentine's Day was written by a Dame Elizabeth Brews in the 15th century.

And, cousin mine, upon Monday is Saint Valentine's Day and every bird chooses himself a mate, and if it like you to come on Thursday night, and make provision that you may abide till then, I trust to God that ye shall speak to my husband and I shall pray that we may bring the matter to a conclusion.

These popular verses further helped to create a romantic image of Valentine's Day festival during the Middle Ages.
Lovers, therefore, began to celebrate Valentine's Day by expressing love to their sweethearts with an exchange of love notes and simple gifts such as flowers - However many other traditions such as the giving of chocolates, or jewellery are actually more modern in way that several large companies advertise that such things are the "perfect gift" for a loved one and over time this became a traditional valentines practice.

The earliest known record of a Valentine's Greeting was sent in the fifteenth century rondeau written by Charles, Duke of Orleans to his "valentined" wife during his holding in the Tower of London following his capture at the Battle of Agincourt, 1415.
In the letter he wrote;

Je suis desja d'amour tanné
Ma tres doulce Valentinée…

Using the language of the law courts for the rituals of courtly love, a "High Court of Love" was established in Paris on Valentine's Day in 1400, shortly after the death of Geoffrey Chaucer. The court dealt with love contracts, betrayals, and violence against women. Judges for the court were selected by women on the basis of a poetry reading.

It was only after this Court was established that Valentine's Day became associated with Romantic Love when the tradition of courtly love flourished with the popularity growing from the poetry verses by Elizabeth and Geoffrey.