Purpose of keys above each Braille key on Braille display

What are the keys on a Humanware Braillant keyboard, the ones found above each Braille key, the ones that look like small knobs that can be made to slide downwards towards the keys and probably slide back upwards on their own when released?

What do these do? Do these slide the positions of the keys on the display by making them sink downwards and then slide back up?