If you observe the payout table of slot machine, you will see that there are different payouts for different played coins. A simple combination can help you to win 10 coins by playing a single coin and 20 coins by playing two coins and 30 coins by playing three coins. The multiplier causes the different payout tables.
Factors of multipliers
Multiplier is nothing but a constant number that is meant for influencing the payout table for every number played. The most common multiplier is x2. It means that you will get more payouts if you play more lines. Some slot machines are there too that can give you more payouts if you play more lines like you can get x8 multiplier which is very profitable.
You can also get some bonus multipliers too with the usual multipliers in some slot machines. If you see that that amount of jackpot is greater than the multiplied ratio of payout then it is because of the bonus. Triple 7' can give you 1000 coins by playing a single line and if you play 2 lines then you can get 2000 coins.
If you know the factors of bonus multiplier and multiplier then it will be easier for you to choose the slot machines. You should remember that you will need to play all lines like three if you play a 3 reel slot machine if you want to have a chance for a jackpot. You can use the multiplier too if you want to check that betting with more lines is beneficial or not.