Citation styles are used for preparation of your list of references (citations) in some special formats. This list also could be named as "Bibliography".
Different journal require list of references in their own format (style).
There is several examples of the same reference just with different style :
 Yue Z, Jiang W, Wang L, Gardner S, Pittman Jr. C. Surface characterization of electrochemically oxidized carbon fibers. Carbon 1999; 37(11):1785-1796.
 Z. Yue, W. Jiang, L. Wang, S. Gardner, C. Pittman Jr., Carbon 37 (11) (1999) 1796.
 Yue Z, Jiang W, Wang L, Gardner S, Pittman Jr. C 1999 Carbon 37 1785
By using SciRef, you can easily set up any citation style what you need.