[todd3834]

With semantic versioning each time the major version changes it signifies a breaking change. If you have an application that breaks from one of those breaking changes you may not see it as a business opportunity to update because it “works” as it is. However, minor version changes can include anything that doesn’t break. So security patches are hopefully added to any major version that is officially supported.

[grzm]

PostgreSQL versioning is similar to semantic versioning, but doesn't follow it precisely. Major versions require a dump and restore (or other transform, such as an upgrade) of the on-disk data. Minor versions are fixes. Prior to PostgreSQL 10, the changes in the second numeric place are considered "major" versions. So, the past 5 major versions are 11, 10, 9.6, 9.5, and 9.4. The most recent versions of each of those are respectively 11.3, 10.8, 9.6.13, 9.5.17, and 9.4.22.