The four card suits that we know today — Hearts, Diamonds, Spades, and Clubs — are a French design from the 15th century, but the idea of card suits is much older. The written history of card playing begins in 10th-century Asia, from either China or India, as a gambling game. That idea found its way to the ancient Muslim world before the 14th century. The oldest known deck of Muslim playing cards, like the playing cards of today, had four suits: Coins, Cups, Swords, and Polo Sticks. These decks of cards then showed up in southern Europe, but because polo sticks were unfamiliar to Europeans, that suit was changed to Scepters, Batons, or Cudgels (a type of club).
Where do the four suits in a deck of cards originate? What do they represent?
As playing cards became more popular, different cultures created their own suits — as well as their own "royalty" cards, sometimes going as high as six different "face" cards. These decks were hand-painted and included intricate designs of both the suits and the royalty cards. As such, they were expensive to manufacture.
In France, Parisian cardmakers settled on Spades, Hearts, Clubs, and Diamonds as the four suits. The first three of these were adaptations of the German card suits Leaves, Hearts, and Hawk Bells (Acorns was the other German suit). Considering that cards were often made for the French upper class, it isn't difficult to understand why cardmakers chose expensive Diamonds over common Acorns.
The French advanced cardmaking by using flat, single-color silhouettes for the suits. These images could be created with simple stencils, making manufacture easy, quick, and inexpensive. These new, cheaper cards flooded the market in the 15th century, caught on in England, and then traveled to America.
It is generally considered an urban myth that the four suits are meant to represent the four seasons, and that the 52 cards represent the 52 weeks of the year. Many numerological and religious explanations of the composition of a deck of cards have been put forth, but these explanations appear to have been created after the fact, perhaps to give deck-holders a reasonable argument that the purpose of a deck of cards is not for gambling.