Simply put, it seems to be, almost a plough that is towed by a locomotive. It anchors an arm into the ground and through the train tracks themselves. As the train moves forward, the arm drags behind completely destroying the track sleepers.
Yep, and IIRC they were used as far back as the War of Southern Succession, aka the American Civil War.
Somewhere, there is(are) a video(s) of a train track destroyer being used. It might be in the World at War Series, I can't recall. Might be the same footage.
There have been several machines designed/built for destroying RR track besides plows pulled by a locomotive, the US made one post-war based on an M48 tank.
Really destroying the track only buys a few days delay, as it can be quickly replaced if the materials are on hand. Clearing and laying the track bed is what takes most of the work to build/fix a RR and is almost impossible to effectively destroy except for bridges and tunnels of course.