When circuit power up capacitor start to charge.
When press push button capacitor change go to the bulb connected transistor base then start to on
While pnp transistor gives feedback to base stay on that transistor
Flow of current third transistor also start to ON so that current flow to ground and prevent to go current to capacitor
That means capacitor discharge
Then press push button again
Base's feedback current go through the push button to the capacitor
When it charge high current drop the capacitor from transistor base current
So the high current feed from capacitor allows to drop minimum current to ON the transistor
So the transistor getting OFF and without feedback it stay OFF
