Tilt Before Turn handle operation means, that when the handle is in the locked position after using the key. It will still allow you to Tilt the window in for ventilation while not being able to fully open it until you use the key again to open the sash mechanism. This is a great feature if extra safety is required when kids might be present without an adult around for supervision. This lets you have the window always locked, but has the tilt functionality freely available for airflow with the key hidden out of sight.