When a person produces any kind of creative work (poem, song, book, article, etc) that work is considered the creator's intellectual property. It is unethical to use someone else's creative work without giving them credit.
Citing your sources allows your reader or audience the opportunity to verify your information or conduct their own research on the topic, if they desire.
By citing sources you increase your credibility with your audience.
When do you need to cite sources?
How to cite sources?
There are several different citation styles that are used in academia. Two of the most common are: