The difference between copyright infringement and plagiarism:
Copyright infringement is using someone else's creative work, which can include music, videos, a movie clip, a piece of visual art, a poem, a photograph, or other creative works, without permission.
Plagiarism is using someone else's work without giving proper credit or the failure to cite the work adequately.
The courts enforce copyright infringement.
Schools enforce plagiarism.
More about plagiarism