You need to cite any ideas, words, or creative works, which you get from other sources (can be print (books, articles, web sites, email), multimedia (films, podcasts, television, radio), data sources, images, live performances, or conversations. You do not need to cite information that is considered common knowledge.
direct quotation: when you copy a source word-for-word
"Good citations should reveal your sources, not conceal them. They should honestly show the research you conducted. That means they should give credit where credit is due, disclose the materials on which you base your work, and guide readers to that material so they can explore it further." (p.4 Lipson, Cite Right, 2006)
paraphrasing: when you closely and accurately summarize the words or ideas of another source in your own words.
Citing properly requires that you provide your sources honestly and clearly so that your readers can understand the basis for your research, check your facts and ideas, and pursue your sources further. (p.4 Lipson, Cite Right, 2006) (Tutorial)
A citation style will provide the format for citing sources and creating the bibliography in your academic work. There are many different citation styles. APA, Chicago, and MLA are common citation styles.