Put simply, referencing is a way for an author to show their reader where they got the information they used in a piece of work.  

There are two things an author must do to properly reference in an assignment:

1. In-text citations. In-text citations are used whenever an author uses an idea or a quote from another source. They don't show the full title of the source; to save on space, they simply show the author's name, the year the source was published, and the page number*. 
   For example: 
   
2. Reference list. A reference list is something that an author includes at the end of a document. It is an alphabetical list of all in-text citations that appeared in an author's work. In the reference list, the full details of each source are provided. For example:
    

Note: reference style. Different places use different 'styles' of referencing. These styles are just a collection of rules about how to set-out referencing. For example, one style might say to put dates in brackets (2019), while another might say to use footnotes**.

Corpus Christi College (and this guide) uses the APA 6th style of referencing.

*Some sources, such as websites, will not have a page number. In this case, use a paragraph number by counting down from the beginning of the page, or an abbreviated heading in quotation marks. 
**2019