In Software Development, apps are versioned by following Semantic Versioning, which is simply a convention that everyone starts to follow.

Angular also follows semantic versioning which has a Major.Minor.Patch format. We increment a specific section when there is a major, minor or patch release:

Major Release The Major part is incremented by one if the new features break backwards compatibility, Minor Release The Minor part is incremented by one if the new features don’t break any existing features, Patch ReleaseThe Minor part is incremented by one 1 for releasing patch fixes.

The Angular team releases a new major version each six months and the last version, as of this time, is Angular 8:

You can follow with the latest versions from the CHANGELOG.