Citations provide information about where you found the ideas that you are quoting, paraphrasing, or using to inform your research. The purpose of citations is to give credit to original creators (authors, performers, organizations, etc.) and to make it easy for others to find the same information that you did.
Plagiarism is the practice of using another person's words or ideas without giving credit to that person (i.e. without citing). In an academic setting (such as college), plagiarizing can result in failing an assignment, course, or even being suspended from the school.
Check out the library's Citations & Plagiarism guide for more information about how to avoid plagiarism, citation styles, generating citations, and more.