updatePolicy for release repositories

I can't seem to find a detailed description of how updatePolicy affects
release repository behavior. Can someone explain or point me to a
document that does?

I'm also interested in understanding how, if at all, updatePolicy
affects release-version range resolution with regard to how often
maven-metadata.xml is checked. Based on experimentation, updatePolicy
does not make a difference in how often Maven checks maven-metadata. It
always downloads metadata for each range expression referenced
dependency. Is there a way to limit range resolution to local
repository contents when running in offline mode? I appear to get
missing dependencies often if I do this.