Citing material -- by including it in a bibliography and by using in text citations -- allows readers to know whose ideas you are using. This gives the original authors credit, and it forms the basis of your own authority as a writer.
The role of a citation is for your reader to be able to see easily where your evidence comes from, and to track down and read or view those materials themselves:
- who is to from? (author name),
- when is it from? (date),
- where is it from? (publication, publisher)
Citation styles are based on disciplines and are a central feature of the scholarly conversation. Part of forming your own authority as a writer is using the citation style correctly -- including things like correct punctuation.