Question: what is the difference between on the bed and in the bed?
Answer: For instance, “in bed” can simply mean “asleep”. ... If you had a book, and it was on the bed, you wouldn't say the book was “in [the] bed”, but “on the bed” even if the book were under the covers. Usually though for people, “in bed” means “inside the bedding-environment” (under the covers), and on the bed is on top of it.