“Extends a private network across a public network”
Have you ever played paper-cup telephone with a friend, where you have a piece of string sending the sound between two cups? That’s a network. The world is the public part. Now your computer can be the string, and you can control both cups.
Keep in mind VPN lets you ELI5 networking into paper-cup telephones.
Now, a lot of people think of the virtual private network as literally (defining a private network), but a lot of VPN involves the encryption of the data. We’re talking about the “private” word there. Which means most things won’t be able to identify or understand what’s going on inside the “private” network. It doesn’t mean they can’t tell you’re the sender. So, I can still see you have one of the paper cups (source -> VPN) and someone at the other end (VPN -> source) has a paper cup. I can still see whether you’re talking (sending data) on the line connecting the paper cups. But because it’s encrypted, I can’t see the data within it.