Whenever you use another person's language, ideas, or other original content, you need to acknowledge this both within the body of your paper using in-text citations and at the end of your paper in the bibliography or reference page.
Your professor will let you know what citation style (e.g., APA, MLA) is required for the assignment. These style variations are usually specific to your discipline or area of study. For example...
APA (American Psychological Association) - commonly used in the Social Sciences
MLA (Modern Language Association) - commonly used for Humanities and Liberal Arts
Use the tabbed options on the left to find the info you need to know regarding how to cite your work properly thereby giving credit where it's due, demonstrating your excellent research, and avoiding the appearance of plagiarism.