@Alfred Armstrong has well explained what the 'master' attachment option stands for, which I understand directly answers your questions. However, for the problem you have outlined, as a temporary solution, to get it to display the Master, go to admin>structure>views>settings, and click "Always show the master display".
Then simply create a new block view, copy the newly displayed info from the Master to this, and go back to admin>structure>views>settings and turn off "Always show the master display" again.