Presenting or closely imitating someone else's work or thoughts as your own constitutes plagiarism. Plagiarism can be intentional or unintentional and can result in significant consequences. The following website suggestions can help clarify the act of plagiarism.
Purdue Online Writing Lab (OWL) - avoiding plagiarism
Plagiarism.org - recognizing plagiarism
Indiana University Bloomington School of Education - plagiarism tutorial, practice, and test