Any ideas, images, or words you do not create yourself must be given proper credit if you use them in your paper, BECAUSE you are using someone else's intellectual property. It shows you have academic integrity and honesty, and helps your readers find your information sources. It shows where your information came from, and adds credibility to your paper.
Below are some of the common citation styles.
Modern Language Association (MLA) documentation guidelines are often used in the humanities fields, including English, comparative literature, literary criticism, and foreign-languages.
This style, developed by the American Psychological Association, is frequently used in psychology, sociology, business, economics, nursing, social work, and criminology.
This style is a simpler version of the Chicago style.