Buck converter
also known as: Step-down converter
A switching regulator that steps voltage down by chopping the input and averaging the result through an inductor and capacitor. Instead of burning the excess as heat, it converts — efficiencies of 85–95% are routine.
In practice
The trade for that efficiency: switching noise, more parts, and layout that matters. The feedback divider sets the output voltage; the inductor and switching frequency set the ripple. For drops bigger than a volt or two at real current, it's the default answer.