In the iPhone general settings. What does VPN mean. And what does it do?

In the iPhone general settings. What does "VPN" mean. And what does it do?

VPN is "virtual private network"

If your workplace supports it, a VPN may give access to the company private network from offsite by creating a secure tunnel to a VPN server and then giving your iPhone an address on the company network. Depending on how things are configured, that might give you access to company servers but nothing else, or might send all your web requests through company filters and monitoring.