Classic slots is a term that can be used to describe a type of video slot and slot machine.
Some of the first slot machines were invented a few decades ago. The gameplay was relatively simple and the design involved three reels and one to three paylines. In addition, the symbols included various fruits, a bell and a shamrock, and in some later machines, a joker.
Today, when someone uses the term classic slots, they are most likely referring to a slot game that resembles those first ones.
Many video slot software developers design new games themed after old vintage slots. While some of them come with a modern-day twist, other titles try to retain as much of the retro feeling as possible, with the only difference being new and refurbished graphics.