For most use cases, you only need to know the required Java SE level for your application to decide which Azul Zulu Prime JVM version to install. For example 8 (also often written as 1.8.0) or 11.
If your application documentation for instance lists Java 1.8.0_291 as requirement, you need to download the latest Azul Zulu Prime JVM version of Java SE level 8 from the Azul Platform Prime download page.
If an application documentation emphasizes a requirement to a specific Java SE update level within one of those three SE levels, like 8u111 (1.8.0_111) with the focus on the 111, the reason for that might be a security fix or a bugfix specifically addressing a Java SE API method used by the application.
The Azul Platform Prime Release Notes contain information about security fixes which were adopted from OpenJDK into Azul Zulu Prime JVM to address a known CVE. Those are listed in the release notes section Common Vulnerabilities and Exposures Fixes.
Major bugfixes regarding Java SE API methods are also listed. If that information is not sufficient and you need more information about the corresponding Java SE update level of the Azul Zulu Prime JVM version you are using, please contact Azul Customer Support.
The version numbering scheme for Azul Zulu Prime JVM follows the numbering scheme used for Ubuntu Linux. For example Azul Zulu Prime JVM version 15.05.1.0 denotes with the first two numbers the major version, here 15.05, where 15 stands for the year 2015 and 05 for the month of May. The 3rd and 4th numbers are the minor version, 1.0 in this example. The version numbering of the optional ZST (Azul Zulu Prime System Tools) is independent from Azul Zulu Prime JVM and Java SE. Generally, all previous Azul Zulu Prime JVM versions can be run on the latest ZST.