An environment groups Power Platform resources such as flows and connections. Separating development, test and production helps prevent a trial edit from acting on production data. The environment selector tells you where you are working, but it doesn't replace a review of each connector destination.
Sharing has different purposes. A co-owner can edit and manage a flow, while run-only access on an eligible instant flow lets someone start it without that editing role. Connected services still enforce their own data permissions and connection behavior. This local designer records an environment and a co-owner list for practice; it doesn't create tenant roles or implement a full administrative policy system. The exercises ask you to configure those visible settings and explain the additional workplace checks rather than claiming a local label grants real security.