Whenever you use someone else's work or ideas.
In general, there are three ways to incorporate information from your sources into your research project:
Each time you have incorporated information from your sources into your paper, you need to cite the source in the following two places:
The style guide will tell you exactly how to format each of these parts of citing, but the idea is the same across all of the styles.
APA and MLA are two of the most common style guides for academic writing and publishing, but there are MANY others (Style Guides). We also have styles for every day citing -- think of the 'PC:@" or "camera emoji:@" in Instagram to give photo credit or think of an online article that links to other articles. These are not the formal academic citing styles from a published style guide like MLA & APA, but they do follow an accepted social guideline for how to correctly give credit to the original creator.