Q. What is a citation?

"A 'citation' is the way you tell your readers that certain material in your work came from another source. It also gives your readers the information necessary to find that source again, including:

• information about the author
• the title of the work
• the name and location of the company that published your copy of the source
• the date your copy was published
• the page numbers of the material you are borrowing"

Source: http://www.plagiarism.org/citing-sources/whats-a-citation/