Using information fairly and acknowledging sources accurately is an essential part of any research project. Citations provide information to help readers locate the sources you use and and provide a way for you to credit other scholars for their original ideas or findings.
To allow readers to trace a cited source quickly and accurately, researchers usually follow a certain citation style. These styles are usually outlined in style manuals.
The citation style you use depends on a variety of factors. Many disciplines tend to use one particular style over another (APA for psychology, for example). Your instructors may require you use a certain style, so ask what style to use before you begin your research. If you are publishing one of your works, your editor may require that you use of a certain style.
If you aren't required to use a certain style, use one that you are comfortable with and that best fits your needs. Just follow the guidelines and be consistent.