Buck regulator output
Your question seems to be "How does a buck converter work?"

To summarize:


The switch is turned on
Vin rises fast but the inductor delays the rise of Vout and it expands it's magnetic field
The switch is turned off when Vout is near/above the desired voltage
The inductor's magnetic field collapses and powers the circuit
When Vout is near/below the desired voltage, goto #1


The fluctuation of Vout due to switching is called ripple. A capacitor is typically added in parallel with the load to reduce ripple.

Specifically:
http://en.wikipedia.org/wiki/Buck_converter