Referencing (or citing) is acknowledging the sources of information that you have used in your written work at university (for example, in an essay or a report, or in your thesis).
Citing a reference acknowledges the work of the author you have consulted and enables others to locate the item that you have cited.
Failure to provide proper acknowledgement of your use of another's work constitutes plagiarism.
To cite correctly, you need to use a referencing style: a standardised way of recording the elements of a book or journal article, or web site.
Most university departments ask you to use a specific referencing style, such as MLA or Harvard (the author-date system.) Check with your department to see if they recommend a particular style.