What does SNAPSHOT mean as opposed to 1.0-SNAPSHOT

[Pete]

I understand that

<version>1.0-SNAPSHOT</version>

means the artifact is still under development, and working towards a
1.0Release.

But what does <version>SNAPSHOT</version>   mean ?

I am trying to understand if it can help when doing a Maven Release using a
manual approach (i.e updating pom versions manually, as the mvn release
plugin still has issues)