Both plagiarism and copyright violation involve improperly using a work created by someone else, but there are differences.
Plagiarism is an ethical and administrative issue for a college student--it can affect your grade, your academic career, and your reputation. Correctly quoting, paraphrasing and citing will make it a non-issue.
Copyright violation is a legal issue--it can lead to financial penalties in a court of law. Keep it legal - cite, acquire permission or pay for use.