A slot is a dynamic placeholder that either waits for content (passive) or calls out to the renderer for content (active). They are used in conjunction with scenarios.

A machine that is capable of generating combinations of symbols on its reels and paying out winnings according to the pay table. There are many different types of slots, some which allow players to choose their own number of paylines while others automatically wager on all available lines. Some also have special symbols which can trigger additional bonus rounds or even jackpot levels.

The first slot machines were invented in the 19th century. The earliest contraptions, created by Sittman and Pitt, had five drums with 50 poker cards. They were operated by inserting coins or paper tickets that contained barcodes. In 1899, Charles Fey improved upon this invention with his Liberty Bell machine. It was the first three-reel slot machine to use a random number generator and is now a California Historical Landmark.