Davies, Martin, "Plagiarism and Paraphrasing" in Study Skills for International Postgraduates, 2nd ed., Bloomsbury, 2022, p. 83-104.
Citing sources correctly is essential in academic writing for several reasons:
Quoting means quoting the author verbatim, that is to say, without changing anything in the text. Any minor change in the text must be put inside square brackets [...]. If you omit a part of the text (ellipsis), this must also be indicated by three dots inside square brackets [...], and the ellipsis must not change the meaning of the text. If you decide to underline a part of the quotation or to bold or italicise some words, this should also be indicated ("emphasis by author"). And of course, the quotation itself must be enclosed in quotation marks.
Paraphrasing means putting someone else's ideas into your own words. It does not mean simply replacing a few words with synonyms. It is generally recommended to change the structure of the text. Of course, the author and the source must be correctly referenced.
It can be difficult to tell whether a paraphrase is too close to the original text or not. This video gives an example of a good paraphrase.
To summarise, you must shorten the original text, keeping only the main points, in your own words, and, of course, the source must be correctly referenced, and the author's thought must not be misrepresented.
Whether you quote, summarise or paraphrase, you must always cite the source, giving all the necessary metadata. And you must, of course, take care not to misrepresent the author's argument.