A VPN hides your traffic from your internet provider, not from everyone
Consumer VPN services are often sold as a cloak of anonymity, but the technology was never built to make anyone unidentifiable. It wraps data in an encrypted tunnel so your internet provider cannot read it. The company running the VPN, and the website at the far end, may still see what you do.
At heart a virtual private network is an overlay: it stretches a private network across a public one such as the internet. A tunnelling protocol carries messages from one machine to another inside an outer wrapper, and encryption keeps eavesdroppers from reading them. A message authentication code can also be attached to each packet, so anything altered along the way gets rejected rather than silently accepted.
Businesses were the original customers. A host-to-network setup lets a remote worker's computer join an office network it cannot physically reach, with each machine opening its own tunnel. A site-to-site arrangement instead links whole networks, such as a branch office and a data centre, with tunnels running only between gateway devices at each location, which then share the connection with every local machine behind them.
Some choices involve trade-offs. Split tunnelling lets a user reach the company network and the open internet at once, saving bandwidth and avoiding constant reconnection, but it can leak domain name lookups and sidestep the company's own security filters. Traditional VPNs are also point-to-point links, so older software relying on broadcast messages, such as NetBIOS in Windows networking, may not work as it would on a local network. Not every so-called VPN even encrypts: trusted VPNs rely on the security of a single provider's network, often using a technique called MPLS, instead of cryptographic tunnels.
Mobile VPNs solve a different problem, keeping a secure session alive as a device hops between cellular networks and Wi-Fi hotspots. Police officers use them to reach dispatch systems and criminal databases from patrol, and they also serve field service crews and healthcare workers.
Source: Virtual private network
