Merriam Webster dictionary defines plagiarism as the act of using another person's words or ideas without giving credit to that person. Learn more by visiting these sites...
http://www.plagiarism.org/ - Includes information about plagiarism, how to avoid it, and how to cite your sources.
http://kidshealth.org/kid/feeling/school/plagiarism.html# - Excellent article explaining plagiarism. Includes a plagiarism checklist
http://owl.english.purdue.edu/owl/resource/589/1/ - Ths Purdue OWL Writing Lab's Guide to avoiding plagiarism
Watch this video on how to use online content responsibly.