A citation indicates to people viewing your work that certain arguments, quotes, or ideas originated from another author's work. Together, your in-text citations and your reference list, show readers how you built your argument.
If you're ever in doubt about whether or not to cite, CITE!
Citing is imperative for anything that is not your own, original thought and for facts that are not common knowledge.
What is common knowledge? Any fact that is widely known.
-George Washington was the first president of the United States.
-Hawaiʻi is the 50th state in the USA.
-Queen Liliʻuokalani was the last monarch of the Kingdom of Hawaiʻi.