A ghostwriter is a person who is hired for writing content on payments. These writers are never credited for the work they do but they charge for their services. But there were cases happened in recent years when these writers were credited by some fiction and nonfiction book writers agency at the name of an assistant researcher of the book.
Moreover, these writers are the most experienced people, they charge amounts for their services in high payments as they are sacrificing the credit of their own written material. It is also assumed that many of the amazing publications of old times can be ghostwritten. But the fact is still unknown.