A way of crediting the sources (books, journals, websites) you have used in your research. Your department may ask you to use either the Numerical or Harvard method of referencing - ask your department for their guidelines.
When you borrow the ideas and/or words of others, and use them in your own essays, you have to acknowledge their original source: you have to reference it. Referencing has two separate elements: the in-text citation or footnote, and the list of references or bibliography. More about referencing.
acknowledge and reference any publication used - or idea quoted or paraphrased - in an assignment. There are numerous Referencing Styles and your lecturer should advise on the preferred style.