A slot machine is a gambling machine with three reels and a lever (or a button in modern machines) the reels spin when you click the button.This kind of games is very easy and very funny all you have to do is insert a coin in the machine and press the button (or move the arm in old machines).
For online casinos this games are enhanced very much because overcoming the mechanical difficulties make it easier to implement more reels online which raise the winning possibilities.
We should also mention that online slot machines have more symbols, options to be played and more bonuses to be won.
One of the most important terminologies for players to be known is "RTP" return to player which is related to the payment percentage.
A small example will make everything clearer :
If we have a slot machine with $1 cost of each spin, after 1000000 spin it will gain $1000000 and if the machine return to the players $950000 and keep $50000 for the house then we said that the RTP of the machine is 95%.
Important point is the slot machines are typically programmed to pay out between 82% and 98% for the players.