what's plagiarism?

Plagiarism is the practice of claiming, or implying, original authorship, or incorporating material from someone else's written or creative work in whole or in part, into ones own, without adequate acknowledgment. The written or creative work which is plagiarized may be a book, article, musical score, film script, or other work. Unlike cases of forgery, in which the authenticity of the writing, document, or some other kind of object, itself is in question, plagiarism is concerned with the issue of false attribution. Within academia, plagiarism by students, professors, or researchers is considered academic dishonesty or academic fraud and offenders are subject to academic censure. In journalism, plagiarism is considered a breach of journalistic ethics, and reporters caught plagiarizing typically face disciplinary measures ranging from suspension to termination. Some individuals caught plagiarizing in academic or journalistic contexts claim that they plagiarized unintentionally, by failing to include quotations or give the appropriate citation. While plagiarism in scholarship and journalism has a centuries-old history, the development of the Internet, where articles appear as electronic text, has made the physical act of copying the work of others much easier.

Provided you write about your opinions in your own words it is not plagarism to write about a popular topic. You can also quote people and list sources provided you let people know that is what you are doing with quotation marks, and by listing the original author. Hope this helps. Cheers!

There's a difference between plagarism, which is copying the words or ideas of another person, and trying to get across something that's considered to be "common knowledge." But, there are different degrees of common knowledge, too, and different degrees of plagarism, which can make things somewhat problematic.