Like other services, Windows lets you save the passwords used for your dial-up and VPN connections. If you forget these passwords and need to use them on another computer, for example, you’ll find they are hidden behind asterisks.
However, you can use a utility, such as Dialupass from NirSoft, to recover them. It can even recover them from a specific phonebook (.pbk) file or from another instance of Windows, such as on an old drive or network computer.
Remember, other people that have access to your computer can also use utilities like this, so you might consider not caching your passwords.