According to the purpose let’s define five main types: Intranet, Remote Access, Extranet, Internet, and Client/Server VPNs. As for Intranet, it is used to combine several branches of the same organization into a single protected network. Remote Access VPN is considered to create a safe link between segments of one corporation/organization and a single user. Extranet VPN is used for those nets which are connected by some ‘external’ customers. The main function of it is considered to be a ‘milestone’ of protection. To learn more about Internet VPN follow the link. And Client/Server VPNs, as you understand from the term, is used to provide qualitative protection to the data that is transmitted between two nodes of a corporate network. On the whole, the common feature is to provide protected connection enhancing the level of security.