Buck regulators, or Step-down regulators take a higher voltage input and convert to a lower voltage output.
Other names for the product are switching regulators, DC-DC converter, and switched-mode power supplies (SMPS). These are much more efficient than simple linear voltage regulators, like the 7805.
For example, if you want to run a 5V LED strip, but your battery is 12V,you can use this to efficiently switch the voltage.
Input voltage: 4V-35V
Output voltage: 1.23V-30V
Input current: 3A(maximum)
Specifications:
Conversion efficiency: 92%(highest)
Switching frequency: 150KHz
Output ripple: 30mA(maximum)