The slide track is for the Simplicity and Simplicity Plus stairlifts.
Like the powered hinge, when the toggle or remote control are activated the Slide Track is enabled automatically.
The Slide Track is a little shorter than your staircases length so when you start to going up the staircase the track will move with you. The track reaches the top of the stairs before the stairlift and stop while the lift moves to the top where you can safely get off. When you go down the stairs the track wil also travel down.
If there is something in the path of the side track it will automatically stop because it has safety sensors all the while still allowing you to move the stairlift towards the object so you can remove the obstruction if safe to do so.