Medion Notebook, Recover D?

I recently bought a Medion notebook. Now to my question, after a short time I got the message that the Recover (D) was full. What is the Recover (D) and what is the Boot (C).

On my old PC, C was the SSD and R the HDD.

Recover is a partition (a piece of your hard drive) that is needed to restore the computer in an emergency.

Better not save anything on this drive.