REFERENCING is a way to demonstrate that you have extended your reading, learning and comprehension by using relevant and up to date sources.
Primary sources refer to material the author has written, like all the works written by Shakespeare.
Secondary sources are written as interpretations, criticism, research, etc. about a subject or an author. An interpretation of Shakespeare’s tragedies will be categorised as secondary material on his tragedies. The tragedies themselves will be the primary sources (Source)
To give recognition to the original author of the text, opinion, idea, fact, image, etc.
To enable your reader to check your information
Sources confirm the completeness of the research
Quotations and references lend authority to the argument, view, etc.
The source list can be consulted by the reader to verify information in the text
The sources can be used by the reader as additional sources to a topic.