Stackoverflow에 있는 명료한 답변입니다.
A snapshot version in Maven is one that has not been released.
The idea is that before a 1.0 release (or any other release) is done, there exists a 1.0-SNAPSHOT. That version is what might become 1.0. It's basically "1.0 under development". This might be close to a real 1.0 release, or pretty far (right after the 0.9 release, for example).
The difference between a "real" version and a snapshot version is that snapshots might get updates. That means that downloading 1.0-SNAPSHOT today might give a different file than downloading it yesterday or tomorrow.
Usually, snapshot dependencies should only exist during development and no released version (i.e. no non-snapshot) should have a dependency on a snapshot version.
그러니까 스냅삿을 정식 릴리즈 버전은 아니고 아직 개발이 진행 중이어서 라이브러리 파일들이 업데이트될 가능성이 있는 겁니다. 쉽게 말하면 안정화 버전이 아니기 때문에 프로덕션 앱에서는 사용하지 않으시는게 좋겠습니다.