How does the track mechanism work? Is that just a string being wound around the motor shaft? I've been playing around with Arduino and find the electronics ea

How does the track mechanism work? Is that just a string being wound around the motor shaft? I've been playing around with Arduino and find the electronics easy but it's really hard to get good information about linear motion in terms of what parts to get and what wheels / accessories are compatible / needed with what tracks. Very few resources out there and I've ordered so many incompatible tracks, wheels, carriages, etc because I couldn't find any information on what mates with what.