What should be referenced:
If it isn't yours...reference it!
Why is APA formatting so important?
Put simply, APA formatting provides a consistent format for reader's to easily comprehend.
The American Psychological Association (APA) created the formatting style which is most commonly used to cite sources within the social sciences. Other formats exist such as MLA, Chicago, and Turabian, however they are commonly used within the humanities.
Every detail such as when to capitalize, when to italicize, what font and size to use, margin widths, and running heads are important because they are a set standard within the scientific community and expected as you advance within the industry.