I always thought the IDT - which Pfaff calls 'dual feed' in all its promotional and sewing machine manuals - meant Integrated Dual Technology.
Anyway, when you view the video you see that little black thing behind the foot on the machine. You can see it grabs the material just like having a set of feed dogs on the top of the material Thus, you have an even feed when that IDT - or black thingy - is in place. If the sewer doesn't want that then it is just lifted out of the way.
It makes sewing much easier for the person using the machine. It also is a much desired assist for those with any hand or finger handicap.
I love mine. I don't think I'd be sewing as much without it.
ali