There is a great new article that the CRM development team posted that I have linked below. This talks about the new CRM Online Sandbox Instances, the labels, and breaks down what they mean and how to set the labels correctly for your Online instance and organization. Also in the article, are some new features that were introduced with the sandboxing.
http://blogs.msdn.com/b/crm/archive/2014/03/20/introducing-sandbox-instances-in-crm-online.aspx