First generation charge pump. Why? Because it worked well for analog circuits. See Wiki for detailed operation of how this works. However, according to [Perigny], this isn't well suited for ICs because stray capacitance is reasonably high. Although not stated in the paper, the other part to that is that capacitors eat up lots of area and so while largish capacitors can be made they are relatively expensive.

In essence, instead of apply, say, an AC signal, one . [Perigny] presumably shows Vin as a separate terminal because you can boost Vin + n * VDD if you happened to have a Vin higher than VDD.

1. Area Efficiency Improvement of CMOS Charge Pump Circuits, Ryan Perigny