I found this circuit online but is not sure how does it work. Can someone explain to me how it works?

 

The left side 22uF capacitor charges to about 11.3V each time the 555 output goes low.
The right side 22uF capacitor charges to 10.0V plus the 11.3V from the first 22uf capacitor each time the output of the 555 goes high so the output becomes 21.3V.