This is a very beginner-ish question. I didn't know where else to ask, or even what terms to search for, so I hope this is the right place.
I'm replacing the logic board on a monitor.
The replacement board came with this gray material covering all the delicate parts (see image; one has the position skewed on purpose).
What is it? Was it for protection in packaging, or is it a heat conducting material?
Should I leave them all, or remove a few?
It's clear that a couple were left on the original board, but not as many as came attached to the replacement.