When you use information from other authors in your writing, you must be honest about revealing your sources. To do this, various formal methods of acknowledging where you gathered information have been developed. This includes both using the exact words or the ideas of another.
Writers value their work.
To steal words and ideas that are another writer's property is grossly unfair. It is intellectual theft. In the past few years, in cases that made headlines, a university president and a newspaper reporter had to resign because of plagiarism. All colleges, schools, and universities, including Austin Community College, consider plagiarism a scholastic offense and punish students for it. To avoid such charges, you must document your writing.