As defined by the University of Utah Student Code, “Plagiarism means the intentional unacknowledged use or incorporation of any other person's work in, or as a basis for, one's own work offered for academic consideration or credit or for public presentation. Plagiarism includes, but is not limited to, representing as one's own, without attribution, any other individual's words, phrasing, ideas, sequence of ideas, information or any other mode or content of expression." (See Student Code B Definitions. 2c.)
The University of Florida's George A. Smathers Libraries have created a series of mini-games to help you understand plagiarism. Start with mini-game 1 and see how you do!