It's a common (usually in the US?), but incorrect, use of the word 'snaffle' to mean a single-jointed mouthpiece. The correct definition of a snaffle is a direct pressure bit, I.e. No shanks, that can actually have any kind of mouthpiece you like.
HOWEVER, there is such a thing as a hanging snaffle that has short 'shanks' ABOVE the bit rings but not BELOW, so as to provide slight poll pressure yet remain a direct pressure bit.
Just becuase it is jointed doesn't make it a snaffle...... there are solid snaffles, but becuase they are solid mouth pieces does that make them curbs? No! If a bit is jointed and has shanks then it is a jointed curb..... if a bit has shanks it uses leverage and therefore it is a curb whether it is jointed or not....
I don't use the term curb bit, rather there are shanked bits and snaffle bits. A curb bit is a bit with shanks. Whether or not the mouthpiece is solid or jointed does not matter. So if you have a bit with shanks and the mouth piece is jointed its a curb.
There are hundreds of different types of these two basic bits.