What is the difference between a Java CPU (7u79) and PSU (7u80) release?
Java SE Critical Patch Updates (CPU) contain fixes to security vulnerabilities and critical bug fixes. Oracle strongly recommends that all Java SE users upgrade to the latest CPU releases as they are made available. Most user should choose this release.
Java SE Patch Set Updates (PSU) contain all of the security fixes in the CPUs released up to that version, as well as additional non-critical fixes. Java PSU releases should only be used if you are being impacted by one of the additional bugs fixed in that version.