A VPN creates a secure network connection over a public network by using encryption and other security mechanisms to ensure that only authorized users can access the network and that the data cannot be intercepted. This makes it an ideal answer as other mentioned technologies like Network Attached Storage (NAS) and firewalls serve different primary purposes. NAS is primarily used for storage solutions, and while firewalls are indeed for security purposes, they don't create tunnels or encrypt data traffic across networks.