Custom Setting visibility

Visibility—Select a visibility of Protected or Public.

• Protected—If the custom setting is contained in a managed package, subscribing organizations can't see the custom setting: it doesn't display as part of the package list. In addition, subscribing organizations can't access the custom setting using either Apex or the API, however, developer organizations can. If the custom setting is contained in an unmanaged package, the custom setting is available through the Enterprise WSDL like any custom object (as if the Visibilitywas Public.)
• Public—The custom setting is available through the Enterprise WSDL like any custom object. You can package custom settings defined as public. The subscribing organizations can edit the values, as well as access them using Apex and the API, regardless of the type of package (either managed or unmanaged).