According to the Oxford English Dictionary, a citation is: 

1. A reference providing information about where a particular quotation, text, etc., is to be found; a bibliographical reference.  
2. The action or an act of quoting or referring to a passage, text, author, legal precedent, etc., esp. as an authority or in support of an argument; quotation. 
3. A cited passage, a quotation.

There are several other definitions, but these three are the ones that relate to reading, writing and research. 

Every citation has two parts.  The in-text citation, which could be a footnote or parenthetical note and are found embedded in the text of the paper or report, and the reference list (also called bibliography or works cited), which goes at the end of the paper or report. 

"citation, n.". OED Online. March 2017. Oxford University Press. http://www.oed.com/view/Entry/33486? (accessed March 15, 2017).

The citation management tools are especially useful when you are working with a large number of citations or when you wish to easily share the citations with others for your project. You will find here the tutorials and tips in using these tools such as Zotero and Mendeley.

• Citation management at UVic: Managing your references

• Open-source citation manager Zotero