Plagiarism  is offering someone else's work as your own, whether one sentence or whole paragraphs, and whether from an internet source, book, periodical, or the writing of other students. It is also dishonest to submit your own paper as original work in more than one course.  Penalties for plagiarism range from failing the assignment to failing the course or suspension from the university, depending on the seriousness of the breach of academic integrity.

This  UBC website offers examples of plagiarism and hints on how to avoid it.

This Dalhousie website offers professors tips on how to detect plagiarism and the use of "term paper for sale" sites

Here is the Acadia plagiarism website