Plagiarism is dishonest because it misrepresents the words and ideas of another as one's own. If you do commit plagiarism, you are cheating yourself. You don't learn to develop and write out your own thoughts. It is illegal under the law of copyright to steal another's words or expressions of ideas. In short, plagiarism hurts you and others.
Plagiarism can be intentional or unintentional.
Intentional plagiarism involves deliberate copying or use of another's words or ideas. Unintentional plagiarism usually results from ignorance of the rules for documenting sources or from sloppy research and note-taking. Even if plagiarism is unintentional, it is still of a violation of the Code of Academic Conduct. When writing a paper try to use your own words the majority of the time. When you do use another person's words, use quotation marks and give credit to the source, either within the text or in a footnote.