Plagiarism means using someone else’s words or ideas and passing them off as your own. Paraphrasing means putting someone else’s ideas in your own words.
So when does paraphrasing count as plagiarism?
Paraphrasing is plagiarism if you don’t properly credit the original author.
Paraphrasing is plagiarism if your text is too close to the original wording (even if you cite the source). If you directly copy a sentence or phrase, you should quote it instead.
Paraphrasing is not plagiarism if you put the author’s ideas completely in your own words and properly cite the source.