Saint Valentine's Day is celebrated on February 14th to honor Saint Valentine, a priest from Rome in the 3rd century who continued marrying couples despite the Roman emperor's ban on marriage. Valentine was imprisoned and later executed for his actions. Today, Valentine's Day is celebrated in many countries with couples expressing their love through gifts, cards, chocolates, and spending time together. Common traditions include exchanging roses, baking treats, and writing love notes with vowels replaced by hearts.