Then each time Windows starts you'll see the unlock dialog (to deny this uncheck "Ask for the password"; this is so called silent start). In the case you'll skip this dialog or you'll enter improper password WinDefender will running in locked mode (and minimized on the system tray). If you'll have entered proper password - WinDefender will also run but in unlocked mode. Alternatively you can select "Bypass loading" in the dialog, so if you have entered proper password WinDefender auto-loading will be cancelled.
Until you have entered the proper password no encryption will act since encryption service depend on the password.
Anytime you can lock WinDefender. This means that no actions or commands will be available until you'll enter the password. For example, you can enter the password at Windows starts (to start encryption) and then lock WinDefender.
After unlocking WinDefender will prompt you with the message how many times were unsuccessful attempts to unlock WinDefender (if at least once).
However you can hide system tray icon. It may be useful when you run WinDefender in silent autostart mode.
Anytime you can see list of files that have been opened in the folders from the WinDefender's list. You may setup your favorite hot-key for quick access to this list (see Preferences)!