I'm going to assume that by double triggers, you mean triggers that are mounted one in front of the other. If so, they are called double set triggers. Their purpose is to provide a light trigger let-off that doesn't disturb the rifle and pull it off target when you fire.
Basically there are two types. The single acting double set triggers must be set before the hammer or cock (if a flintlock) will stay in the full cock position. These are best used on target rifles since they must always be fired from the "set" or very light to hair trigger position. They are set by pulling the rear trigger first.
The double acting double set triggers are also set by the rear trigger and fired by the front trigger, but the rifle can be cocked and fired without setting the trigger as well as with it set. This is a great advantage when hunting on a cold day and your fingers are a bit numb. With both types of set triggers there is a small screw between the two triggers that adjusts the weight of pull allowing for very light to more firm let-off as the situation requires. To my mind, for all but the dedicated target rifle, this type of trigger is best. It works fine as a target trigger and definitely is the way to go for the hunter.
There's no need to concern yourself about asking a good honest question. Welcome to the forum. :hatsoff: