When you hear the word Slot, your first thought is probably about a machine that spins reels in a casino. Although slots have a reputation for being arcade games played by old ladies, they now account for almost 85 percent of gambling profits. The rise of online slots has further blurred the line between playing for real money and play-money.

In computer science, a slot is an open or closed site in the body of a computer that accepts printed circuit boards called expansion cards. These slots are not to be confused with bays, which are sites within a computer that hold disk drives.

While the majority of slots are still mechanical, a few have become highly mechanized and completely electronic. These machines accept cash or, in “ticket-in ticket-out” models, paper tickets that contain barcodes that activate the machine when inserted. Regardless of the type, most modern machines have a computer that keeps track of each spin’s outcome and records payouts, credits won, and other information.

The number of symbols on a reel, their frequency, and the probability that a particular symbol will appear on a payline are important when choosing a slot game. Volatility is also a consideration. A low variance slot pays out small winnings frequently; a high volatility slot may not pay out for long periods of time, but when it does the wins are large.

Bonus features can make a slot game more exciting and increase the player’s chances of winning. Often, these will involve a minigame or require the player to select a hidden object in order to win a prize.