ie, Voltage at non-inverting termnal = bVsat = [R2/(R1+R2)]Vsat
On the other hand at the inverting terminal, the capacitor tries to charge to +Vsat, which is available to the capaciror through 'R'. but on the way to +Vsat, when the capacitor reaches at a potential equal to the potential at the non-inverting terminal of the op-amp.
ie, when Vc = bVsat.
Since the op-amp behaves as a comparator circuit, the output changes from +Vsat to -Vsat, because the inverting potential is greater than non-inverting potential.
Now, the output is -Vsat, the feedback voltage reverses the polarity to -bVsat, which is available at the non-inverting terminal of the op-amp. The capacitor holds a voltage of +bVsat initially at the begining of the second stage, since the output voltage Vo = -Vsat which can flow to the capacitor. Due to this potential the capacitor tries to discharge to a maximum of -Vsat, but on the way to -Vsat, when the capacitor reaches a potential equal to the potential of the non-inverting terminal of the op-amp.
ie, when Vc = -bVsat.
The comparator circuit changes the output voltage from -Vsat to +Vsat. Which will repeat in cycles.