The four card suits
A standard deck uses the four French suits: spades ♠︎, hearts ♥︎, diamonds ♦︎ and clubs ♣︎. Hearts and diamonds are printed in red, spades and clubs in black. Unicode has two styles of each: the "black" suits ♠︎ ♥︎ ♦︎ ♣︎ are filled, and the "white" suits ♤ ♡ ♢ ♧ are outlines.
Most games treat the suits as equal, and in poker they do not rank against each other. Bridge does rank them, from lowest to highest: clubs ♣︎, diamonds ♦︎, hearts ♥︎, spades ♠︎. Online poker sites often offer a four-color deck, with blue diamonds and green clubs, so the suits are easier to tell apart at a glance.
Playing card characters
Beyond the suit signs, Unicode has a Playing Cards block with every card of the deck as its own character, from the ace of spades 🂡 to the king of clubs 🃞, plus jokers 🃏 🂿 🃟 and the card back 🂠. Each suit also has a Knight card between the Jack and the Queen for tarot-style decks, which is why the codes skip a step. Only 🃏 is a standard emoji, so the other cards appear as text and can look small or be missing in some fonts.
The suits double as decoration: ♥︎ and ♡ are everyday hearts (see the heart symbol page), and ♦︎ ◆ are popular diamond shapes (see the diamond symbol page). For another classic game, see the chess symbols.
How to type card suits
On Windows, hold Alt and type on the number pad: Alt + 3 ♥︎, Alt + 4 ♦︎, Alt + 5 ♣︎ and Alt + 6 ♠︎. On a Mac, open the Character Viewer with Control + Command + Space and search "suit". On iPhone and Android, the emoji keyboard has ♠️ ♥️ ♦️ ♣️ among its symbols.
In HTML, use ♠, ♥, ♦ and ♣. In LaTeX, use \spadesuit, \heartsuit, \diamondsuit and \clubsuit; note that LaTeX draws the heart and diamond as outlines by default.