Take a 240V 60Hz AC source and convert it into a 12V DC signal.
The 4 diode bridge restricts the current flowing backwards, giving you the half-cycle DC waveform. The 2 capacitor in parallel & single inductor acts as a filter that gives you that almost flat DC signal.
Expect the voltage at the lamp to be slightly lower than 12V, because of the diode's small resistance and the LC reactance.
