Cards are 52 rectangles of stiff paper, or cardstock decorated uniformly (to ensure indistinguishability) on one side, on the other, divided into four "suits" of thirteen cards each, numbered from two to ten, plus a jack, a queen, a king, and an ace.
Cards are randomized via a physical process called "shuffling," which can be realized via a number of techniques. Proper randomness is achieved by seven "shuffles."
Although a number of different games involving any number of players and cards (e.g. poker, "go fish") are possible, there is a long tradition of four player games, where each is dealt thirteen cards (i.e. a quarter of the deck). Usually, one suit is declared "trump" (i.e. it dominates cards of any other suit, no matter their value), and play proceeds as players lay down cards sequentially. Every four cards constitute a "trick" which one player wins and keeps for himself. Games in this tradition include whist, bridge, spades, and hearts.
I appear to be a member of the last generation for which the above is common knowledge. Casual questioning of average samples of those not ten years my junior reveals (i) the general assumption that card games are simply a subset of computer games, (ii) uncertain knowledge about the constitution of a deck, and (iii) a vanishingly small understanding of appropriate randomization procedures.