What is this VPN setting good for?
Is it used for remote machine access? How to configure the VPN setting?
It is the same use of using VPN with desktop computer. You can connect to a network and become a part of it to access its resource.
VPN stands for Virtual Private Network, which means that you can join a network (typically a organisation's LAN/WAN) through Internet and access its resources link printing or accessing intranet web portals etc.
As you has asked, it can be used for remote access for computers which are not exposed to Internet and are connected to LAN only.
You can see this link for more information.