Explain about VPN server?

A VPN server is normally a conventional server that has VPN server software installed and configured. It does, however, have a greater number of logical and physical communication ports. The VPN server connects remote and/or local VPN clients and delivers VPN services. For connectivity and communications, the VPN server usually employs one or more protocols, such as point-to-point protocol (PPP). Before being allowed VPN access, the VPN client must first connect to the VPN server and authenticate itself.