Most academic writing cites others' ideas and research, for several reasons:
Different academic disciplines prefer different citation styles, most commonly APA and MLA styles. Besides these styles, there are Chicago, Turabian, AAA, AP, and more. Only use the most current edition of the citation style.
Ask your instructor which citation style he/she wants you to use for assignments.
To avoid plagiarism, provide a citation for ideas that are not your own:
You do not need to cite common knowledge (ex. George Washington was the first President of the United States.) or proverbs unless you are using a direct quotation. When in doubt, cite your source.
Many thanks to PSCC Libraries' excellent APA guide for sharing much of the content and organization.