VPN is a way to join a LAN without having the physical connection to a LAN. It is basically a tunnel through the Internet. One end of the tunnel is at your computer or LAN. The other end of the tunnel is in the target LAN. The tunnel allows data to flow from one LAN to the other as if they were physically joined as one LAN.
A typical use to illustrate:
When I am at work my laptop is part of the LAN. I can go anywhere I want in the system from my laptop. When I go home I can no longer access the company computers across the Internet. From home all the computers in the company are behind a singe address on the Internet. And there are firewalls to prevent anyone from getting to those machines from the Internet, even me.
So I use a VPN connection. My laptop initiates a connection with the address that my work network is behind. The routers/firewalls recognize the request as a VPN connection and routes it to a server that receives the request and authenticates my right to create the connection. Having approved the connection the VPN connection is made. Now I have a VPN tunnel from inside my home network, through my router, through the Internet, through my work router, and into my work network. My laptop is now connected to my work network as if I had gone to the office and plugged in a patch cable to the wall despite the fact that there is the big bad Internet between my house and my office.
The VPN connection is encrypted communication and the computers on each end of the connection communicate only with each other for the purposes of the connection. Nothing is 100%, but this is considered a "secure connection".
Josh
<a target="_blank" href=http://www.jdharm.com>www.jdharm.com</a>