Since you asked about what a snaffle is, here is a quick definition.
A snaffle is a bit that does not provide leverage. In a snaffle, if you put 3 pound of pressure on the reins, the horse will feel three pounds of pressure on its mouth. A snaffle can have any mouthpiece (though it is a misconception that any bit with a broken mouthpiece is a snaffle), but it will NEVER have shanks. Be careful, because many websites and magazines label curb bits as snaffles, which is very incorrect.
A curb, on the other hand, uses leverage (poll pressure, as well as chin pressure when a curb strap is used). So, if you put three pounds of pressure on the reins, the pressure the horse feels will be magnified. How much the pressure is magnified depends on the length of the purchase and the shank.
Hope that helps and was understandable.
I like the bit pictured, as well as a loose ring French link. If your horse doesn't like the movement of the loose rings (mine doesn't) you can go for an eggbutt, dee or full cheek. My preference is a full cheek.