A Virtual Private Network (VPN) is a way to use a public telecommunication infrastructure, such as the Internet, to provide remote offices or individual users with secure access to their organization's network. A private network can be constructed with an expensive system of owned or leased lines that can only be used by one organization.
Wide Area Networks (WANs) are built to provide communication solutions for organizations or people who need to exchange digital information between two secluded locations. Typically, a WAN consists of two or more Local Area Networks (LANs). Computers connected to a Wide Area Network are often connected through public networks, such as the telephone system.
Leased line is referred to as a private line. A leased line is obtained from a communications company (NTL) to provide a transmission medium between two points. The line consists of a permanent dedicated circuit between two points, or to set of previously arranged points. The cost of the line is usually based on the distance between locations. This is in contrast to switched or dial-up lines, which can be connected to any point on the network.