Windows 7 supports different password-based and certificate-based authentication protocols that can be used for both dial-up and VPN connections. Windows 7 first tries to use the most secure authentication protocol that is enabled and then falls back to less secure protocols if they are available.
VPNs allow users to make secure connections to remote networks over the Internet. VPNs create like secure tunnels that allow specific authorized users from the Internet to access corporate internal resources such as, shared folders, printers, databases, etc. In Windows 7 you can configure a connection to use a specific VPN protocol or let Windows automated process. By default, Windows 7 sets the VPN type to Automatic.