This policy setting enables or disables networking in the sandbox. You can disable network access to decrease the attack surface exposed by the sandbox.
If you enable this policy setting, networking is done by creating a virtual switch on the host, and connects the Windows Sandbox to it via a virtual NIC.
If you disable this policy setting, networking is disabled in Windows Sandbox.
If you do not configure this policy setting, networking will be enabled.
Note that enabling networking can expose untrusted applications to the internal network.