A citation style is a set of rules for how to create a source reference. No matter how you refer to sources, do it consistently and according to a single quotation style. There are many different styles of citing, at Rotterdam University of Applied Sciences, APA is the most used one. Other styles used are: IEEE, MLA, Harvard and Guidelines for Legal Authors.
Which citation style?
Which citation style you use depends on your subject area. Not sure which rules apply to your source reference? Ask your lecturer for advice, he or she will be aware of the rules that apply within your study programme.
Guidelines
Each style has its own specific rules.