Question about germinating and rockwools

so i am reading this part on germinating '' Rockwool has a fine germination climate for the seeds. Remove the cover as soon as the seedlings reach above the medium.''

and i find it confusing, so here are the questions

1 wen it says ''remove the cover'' does it mean the rockwool?
2 isnt it risky and hard to remove the rockwool with roots in them?
3 what does it mean wen it says ''remove the cover as soon as the seedlings
reach above the medium'' what is above medium?

i didnt pay that much attention in english class you see, thanks in advanced

Remove the cover is referring to whatever you have "covering" you seeds. You would not ever tear the rock wool off.

Ya by the cover it could refer to a humidity dome in which ur seedlings could be in with the rockwool.

U never try remove the seedlings from the rockwool as one of the biggest advantages of rockwool is that u can plant it straight into ur medium once u see the roots popping out of it

oh and above the medium could refer to the rockwool itself or the medium of ur choice such as soil