Once installed and properly configured, the Protected node module adds a field set in the node edit form (assuming the user has the corresponding permission: "edit any password" or "edit password <node type>".)
This field set includes two flags, a password, and emails (optional.)
By default, the field set is closed unless you selected protected by default. Whether the field set should be opened or closed can selected in the node type settings.
The first check box is used to password protect the node. When checked, the password is required for people who have permission to access the node, but cannot bypass the password in some way (i.e. view, bypass or UID=1 permission.)
Note that this flag is not shown if the node type is marked as Always protected. In that case, it is assumed to always be selected and therefore there is no point to give the user the choice.
The second check box defines whether the default forms have permission to show the title of the node. This is also used to show or hide the title from other modules (such as the Views). This may not work in all cases (i.e when you include tokens.)
The two passwords are shown except when the Global password only option is selected in the global settings of the module. The passwords are required unless you accept a Global password. If required, the node cannot be saved until entered.
The global settings can be used to select whether the JavaScript password strength display should be shown or not.
By default, no email field appears. When you select that option in the global settings, you also get a text area where you can enter any number of email addresses1 that should be notified about the page and password.
Note that when you enter one or more email addresses, it is required to enter the password2. This is because to send the password in clear in the email, you have to re-enter it (the module saves the password encrypted in the database.)
Note that instead of entering a password yourself, you can ask the module to generate a password for you (see the global settings.) In this case, I suggest you enter your own email address if you want to know what the password ends up being.
When you are using the Global password facility, the password cannot be sent using the [node-password] token. Instead, you have to enter the password in the email in the Global settings which means it will be saved in clear in the database.
WARNING
Remember that in most cases emails are sent unencrypted (i.e. totally clear text.) This module does not offer encryption support and thus the password will be sent in clear text. Use at your own risk!