To paraphrase means to reword, generally in a shorter or more easily understood form than the original.
This tool is generally benign, as most authors simply want to give the gist of someone's ideas correctly. However, paraphrasing can also lead to misrepresentation. Frequently, a writer who is using a paraphrase innocently misunderstands the original quote, or simply shifts the meaning too much without intending to do so. Sometimes, however, parapharase is intentionally used to change what the author originally meant. Good writers, editors and readers should be on the alert for authors who are deceitful in how they paraphrase.