Legal case citation, though subject to an amount of variance, follows a general pattern illustrated by the following example:
Apple v. Banana, 21 Mk Blv 986 (2021).
That means the case involved the parties Apple and Banana, and it can be found in volume 21 of Make Believe, page 986, and that it was decided in 2021.
To use an example from real life:
Miranda v. Arizona, 384 U.S. 436 (1966).
So, Miranda was one, and the State of Arizona was the other. It's in volume 384 of the United States Reporter, page 436, and it was decided in 1966.
Some volumes have multiple series, so you'll see something like Cal App 3rd, which stands for the California Appellate Reporter, third series. In many instances, these indices are not government sponsored, but rather are compiled by third parties. Because these works are not protected by copyright, anyone can print them, and so there are often competing volumes. In such cases, it is customary to site important cases in several or even all of the major reports for the jurisdiction.