The reels are the main component of any slot machine. A reel is basically a wheel with symbols painted on it. When you click the Spin button, the reels spin around and eventually stop in a particular position.
The symbols on a slot machine can really be anything at all. They are often related to the theme of the slot machine game. Dolphin Tale, for example, has an underwater theme; symbols include dolphins, fish, clams, crabs, shrimp, and octopuses. Common symbols on many slot machines include cherries, playing cards, the number 7, and the bar symbol.
A payline is a line that runs across all the reels. A payline may be horizontal, diagonal, or zigzagged. When you bet on a particular payline, you are said to have “enabled” that payline. You win at slots when the winning symbols appear on a payline that you have enabled. Some modern online slots games employ Ways To Win, allowing a winning payout whenever matching symbols appear on adjacent reels, instead of paylines.