These are citations that will lead you to the text of a judicial opinion as it can be found in a court reporter. The information contained in a citation for court opinions found in a reporter varies very little.
The citation will always start with shortened versions of the names of the parties to the case, for example: Johnson v. California,
Then it will give you information on which reporter, or publication, contains the text and where in that reporter to look for the text of the decision (the volume number and pages). It also contains information on which court, or jurisdiction, heard the case and what year this opinion was delivered.
321 F.3d 791, 793 (9th Cir. 2003)
volume reporter start pg pg cited jurisdiction date of decision
The reporter and jurisdiction, and sometimes even the party names, are abbreviated. In order to find out what the abbreviations stand for, try consulting either the Bluebook or the ALWD citation manual.