Pedantic, but the word you're looking for is proxy, not VPN.
A Virtual Private Network is a private network such as a Local Area Network created virtually on a Wide Area Network such as the internet. Tailscale, SoftEther, or Hamachi for the old boys are examples of VPN implementations.
A proxy is a server that accepts and forwards traffic from clients through it, lending its IP address to clients as the traffic origin if desired.
A proxy can exist in a private network, but it is not a requirement.
A Virtual Private Network is a private network such as a Local Area Network created virtually on a Wide Area Network such as the internet. Tailscale, SoftEther, or Hamachi for the old boys are examples of VPN implementations.
A proxy is a server that accepts and forwards traffic from clients through it, lending its IP address to clients as the traffic origin if desired.
A proxy can exist in a private network, but it is not a requirement.