Quoting
Example from plagiarism.org:
Original
In his essay, “United Shareholders of America,” Jacob Weisberg insists that “The citizen-investor serves his fellow citizens badly by his inclination to withdraw from the community. He tends to serve himself badly... by focusing his pursuit of happiness on something that very seldom makes people happy in the way they expect it to.”
Summary
“He tends to serve himself badly...by focusing his pursuit of happiness on [money].”
The brackets around the word [money] indicate that you have substituted that word for other words the author used. To make a substitution this important, however, you had better be sure that [money] is what the final phrase meant -- if the author intentionally left it ambiguous, you would be significantly altering his meaning. That would make you guilty of fraudulent attribution. In this case, however, the paragraph following the one quoted explains that the author is referring to money, so it is okay.
From "Quoting Material", Plagiarism.org, 2017, https://www.plagiarism.org/article/quoting-material.