ON. The analog signal (continuously changing voltage signal) moves up and down, but at time "T2" it is clear that it is above the threshold. Exact measurement is not needed.
Analog signals usually continuously change their value. The information they convey is contained in the exact value at any instant.
However, by using a threshold, a signal can represent binary data ("on/off" data). Such a signal is called binary signal.
It is easy and fast to determine if a voltage is above or below a threshold. The signal in the figure is "off" at time T1 and then "on" at time T2.
Is is clear that the signal is "off" at time T1 and "on" at time T2?