The answer should be surprising. Moreover, it is short: virtually nothing.
However, there are reasons why the two terms in the media again and again juxtaposed – and thus: confused by inexperienced readers in or put into a common, mental drawer: There is the Guttenberg Affair, in the course of which the political opponents of the Freiherrn, not a few in number, endeavored to prove to him not only multiple plagiarism, but also speculated on the use of a ghostwriter. However, both theories can hardly be reconciled, because any mediocre ghost writer would have done a better job.
Another reason why the use of ghostwriters is always brought close to plagiarism is the scientific-ethical perspective: Who spends a work written by ghostwriters as own, for example, to pretend an exam can be guilty of fraud. On the other hand, anyone who uses foreign texts without labeling, whether due to carelessness or calculation, is also scientifically questionable.
Ghostwriters do not plagiarize
From this perspective, however, to derive an equation of “ghostwriters” and “plagiarists” would be fundamentally wrong. For as gullible as the use of ghostwriters may be in examining relevant work – the ghostwriters themselves earn their money with scientific work and would hardly find buyers if they would deliver plagiarism.
However, care must be taken with extremely low-priced agencies, which may have an obscure construction with foreign parent companies: this is often a writing that has little to do with the seriousness of serious agencies:
It may be that the authors are students who work at student prices and endeavor to fill many pages as quickly as possible, if necessary by taking over texts from the Internet. This has nothing to do with real academic ghostwriting.