A VPN can extend access to a private network (one that disallows or restricts public access) to users who do not have direct access to it, such as an office network allowing secure access from off-site over the Internet.
The benefits of a VPN include security, reduced costs for dedicated communication lines, and greater flexibility for remote workers.
A VPN is created by establishing a virtual point-to-point connection through the use of tunneling protocols over existing networks.
Virtual Private LAN Service (VPLS) is a way to provide Ethernet-based multipoint to multipoint communication over IP or MPLS networks. It allows geographically dispersed sites to share an Ethernet broadcast domain by connecting sites through pseudowires. The term sites includes multiplicities of both servers and clients. The technologies that can be used as pseudo-wire can be Ethernet over MPLS, L2TPv3 or even GRE. There are two IETF standards-track RFCs (RFC 4761 & RFC 4762) describing VPLS establishment.
VPLS is a virtual private network (VPN) technology. In contrast to L2TPv3, which allows only point-to-point layer 2 tunnels, VPLS allows any-to-any (multipoint) connectivity.