VPN means  a secure and private network which can be achieved using encryption over a public network, typically the internet. Full form of VPN is  virtual private network which  can be extended a private network across a public network and can enable users to send and receive data across shared or public networks as if their computing devices are directly connected to the private network. Applications which are running across a VPN can get benefit from the functionality, security, and management of the private network. Encryption being a common, although is not an inherent, part of a VPN connection. VPN technology had been built to provide access to corporate applications and resources to remote users, mobile users, and to branch offices. For security, the private network connection may be established using an encrypted layered tunneling protocol, and users are required to pass various authentication methods to gain access to the VPN. A VPN has created by establishing a virtual point-to-point connection through the use of dedicated circuits or with tunneling protocols over existing networks. A VPN which is available from the public Internet provides some of the benefits of a wide area network (WAN). From a user perspective, the resources available within the private network may be accessed remotely. Three broad categories of VPNs do exist, and they are remote access, intranet-based site-to-site, and extranet-based site-to-site.While individual users most frequently can interact with remote access VPNs, businesses make use of site-to-site VPNs more often. VPNs are characterized as host-to-network or remote access by connecting a single computer to a network or as site-to-site for connecting two networks. In a corporate setting, remote-access VPNs can allow employees to access the company’s intranet from outside the office. Site-to-site VPNs allow collaborators in geographically disparate offices to share the same virtual network.