A multiplier slot machine has several different pay-lines that can be active. The more lines you play the bigger the prize will be when you hit a winning line. The only way to win the full jackpot on this slot is to hit the jackpot symbols while all pay-lines are active.
On a machine like this you might be paid out at x amount the prize for the first coin and will go up in the same amount of increments for each added line. When you play all lines the multipliers will go up much more then if just playing several lines. For example, 2 coins might pay out 200x and 4 coins 500x but if you play all 5 lines your multiplier is 1000x. You will only need to bet one coin on each line as betting more than one coin has no effect on the payouts.