Interface

In the panel you'll find a path box and two buttons.
In the path box you can set the default folder for the file browser to open in.
The buttons are Backup and Restore, which do as they say.

In preferences you'll find the same path box as in the panel, a checkbox, and a text box.
The checkbox is an option, enabled by default, which saves your userpref.blend file inside each backup, so it can be restored manually just in case the regular restore somehow fails.
The text box is for the panel category, which tab of the sidebar the PowerBackup panel should go, default PowerSave.

When you click Backup or Restore, a file browser will open.
On the right side of the file browser, you should see a bunch of options.
If not, click the button with the gear icon in the top right, and they should show up.
These options consist of two categories:

Blender Preferences

• Editing / Animation
• Experimental
• Filepaths / Save & Load
• Input / Navigation
• Keymap
• System
• Themes
• Interface / Viewport
• Startup File

Some preferences share the same tickbox, this is because under the hood, they're the same.

Addon Preferences

• For Backup: a list of all enabled addons.
• For Restore: a list of all installed addons present in the selected backup file.

This includes addons that have no preferences, so that it at least can enable the addons.

Note

Take a look at the FAQ as well for more information.