Virtual private networks, also known as VPNs, are networks based on public infrastructure (like Internet) to provide remote workstations with secure access to the company's network.
This network does not need to be located in a single physical location (such as the local area network) therefore it is very useful for large organizations that have offices in several cities and need to convey data from one node to another.
VPN manages to remain private by using encryption and additional security measures, so that the information sent seems to be scrambled to any outsider.