Plagiarism - When you present someone else's work or ideas as your own.
Plagiarism can be accidental or intentional cheating. Plagarism is taken seriously as a form of academic misconduct, and it is important to make sure that you acknowledge when information you are presenting comes from other people or authors. Citations are an essential part of your paper or presentation.
Plagiarism can be:
Take a look at Quoting and Paraphrasing, and Integrating Sources into your Paper for more guidance.