A narrow opening, notch, or groove in which something can be inserted. In computing, a position in a series or sequence (such as a job or time slot) that can be filled by a certain kind of object. Also, a slot in the wing or tail surface of an airplane that provides air flow over an auxiliary device such as a flap or an aileron.

In the vast showroom where the machines are displayed, well-dressed men and women push buttons and pull levers while watching cherries and sevens spin on liquid crystal displays. They may be there to play a few rounds of video poker or to test out new machines in an effort to find the next big jackpot. But despite the glitz and flash, these are not people playing for fun. These are professionals, testing and tinkering with machines that can make or break their livelihoods.

While no one has uncovered the Platonic ideal of the slot machine, there are certain principles that undergird most games. There is a vague aesthetic uniformity—colors tend toward primary or pastel, franchise tie-ins are a given, and the soundtracks are typically in a major key. Then there are the rules: 15 coin payouts are standard, and a player can win on multiple lines—linear, diagonal, or even zig-zagged. In fact, modern slots often include so many possible winning combinations that without the lights, sounds, and celebration, most players would have a hard time recognizing their wins.