What Is a VPN, and How Does It Work?
When you switch it on, a VPN creates an encrypted tunnel between you and a remote server operated by a VPN service. All your internet traffic is routed through this tunnel, so your data is secure from prying eyes along the way. Because your traffic is exiting the VPN server, your true IP address is hidden, masking your identity and location.

To understand the value of a VPN, it helps to think of some specific scenarios in which a VPN might be used. Consider the public Wi-Fi network, perhaps at a coffee shop or airport. Normally, you might connect without a second thought. But do you know who might be watching the traffic on that network? Can you even be sure the Wi-Fi network is legit, or might it be operated by some nefarious individual? 

If you connect to that same public Wi-Fi network using a VPN, you can rest assured that no one on that network will be able to see what you're up to—not other users snooping around for would-be victims, nor even the operators of the network itself. This last point is particularly important, and everyone should keep in mind that it's difficult to tell whether a Wi-Fi network is what it appears to be. Just because it's called Starbucks_WiFi doesn't mean it's really owned by a well-known coffee purveyor.

https://uk.pcmag.com/features/88655/what-is-a-vpn-and-why-you-need-one