Cases are the published opinions of courts. They are published in serial publications called reporters. Case reporters may be published by either government publishers (i.e. U.S. government) or by commercial publishers (i.e. West). If a case is printed, the print reporter must be cited, even though the case may be available in electronic formats.
To find a case in a print reporter series or to Shepardize a case, you must have a citation. The citation tells you where to find the case in the series.
A citation will also help you find the exact document quickly when searching a legal database like Westlaw or a free online legal research site.