The quinella is a favorite of low-risk gamblers, because it's a straighforward, no-nonsense bet. A quinella is basically an exacta box with a lower payout, because you pick two horses that can finish either first or second in the race. For example, you could pick Dialed In and ArchArchArch, so at the counter you'd say "1-8 quinella" and pay out $2.
Generally, a quinella is a $2 bet, but you can make the wager in any amount when you get to the counter. You can also do a quinella box, which means you are unsure between three or more horses. The payoff on these is not amazing, but they help guarantee a more likely return on your investment.
Experienced bettors will play the odds on these, seeing where the money is going on the board and betting on mid-range horses to surprise the crowd and come in first and second. When no one is betting on the horses you select, a win could pay off huge amounts of money with just a $2 bet at stake.
Good luck with your quinella bets today!