A style can govern the whole layout of your work e.g. margins, font, spacing, alignment etc. A particular style is often used by a discipline and publishers within it. Getting familiar with a style will serve you well for the future. Always check which style to use with your Lecturer/School.
Websites and books for some of the main styles are listed below:
Consult UCC’s Harvard Referencing Guide for the version of Harvard used in UCC. This guide follows the standard version found in the book Cite Them Right by Richard Pears and Graham Shields (hard copies located in the Boole Library on Q+3 floor at 808 PEAR).