what you see in the middle of the 2 tracks is the rack and the pinion is under the train/coach.
Now the pinion clutches on to the rack and due to the rotational motion(teeth is designed as such), the rack moves ahead. In short rotation motion is converted into forward motion.
please wait...Translate to EnglishYo, what you peep in between them tracks is the rack, and the pinion be right under the train/coach. The pinion grabs onto the rack, and 'cause of the way them teeth are designed, the rack starts moving forward. Basically, we're converting that rotational motion into some straight-up forward motion.