In a nutshell, it is your lockscreen.
PIN, pattern, face, password locks or the default lock (slide to unlock), but it is your lock screen.
Keyguard basically refers to the code that handles the unlocking of the phone. it's like the keypad lock on your nokia phone a few years back just with the utility on a touchscreen.
you can find more info it you look in android/app or com\android\internal\policy\impl
Good Luck !
The lock screen works without keyguard i have tested it. The home button stops working and you can't get to task manager by holding the home key. I wish they didn't develop a new process when it used to be built into system ui or whatever. I don't see the need for the change and extra process
Yes, I also found it here: http://developer.android.com/tools/testing/activity_testing.html It's seems a key-input protection mechanism which includes the screen-lock, but not only includes it. According to this webpage, it also defines some key-input restriction for auto-test framework in Android.
Source: Stackoverflow.com