I am a bit confused about the meaning of a Maven Snapshot and why we build one?
This is how a snapshot looks like for a repository and in this case is not enabled, which means that the repository referred in here is stable and there's no need for updates.
...
lds-main
LDS Main Repo
http://code.lds.org/nexus/content/groups/main-repo
false
Another case would be for:
true
which means that Maven will look for updates for this repository. You can also specify an interval for the updates with tag.