Ghostwriting is a practice in which one person writes and another person gets credit for it. Generally speaking, ghostwriting allows writers to get paid for work up front instead of waiting for royalties or anything like that.
I currently have a job ghostwriting kids stories set in Minecraft, and after a bit of investigation, it seems likely that the author who will get credit doesn't actually exist. There are three signs of this: first of all, he goes by first name and last initial, e.g. Adam A. (not actual name). Secondly, his author description is full of sappy, general statements: "Every day is a new adventure for" him and "He loves writing unofficial Minecraft books for kids." Thirdly, his profile picture is a stock image-- a reverse image search of the profile showed the stock image website it originally came from and websites around the world using the same picture.
I suppose that as far as I'm concerned, it's a contract-enforced pseudonym.