On the home screen or the on-screen keypad (or the control panel itself), READY indicates that all of the security system's sensors are in a normal condition or have been Bypassed. No protected doors or windows are open* and no alarms are in progress. 

Note that the system can show READY when it is running on battery backup during a loss of AC power. 

*If door or window sensors are open, but have been properly Bypassed, they will not prevent the system from showing Ready.