This is a DC/DC step-down voltage regulator that converts input voltage between 3.2V and 40V into a smaller voltage between 1.25V and 35V, capable of driving a 3A load with excellent line and load regulation.
In some projects, you might need different voltages (3-35V) for your devices. This module can speed up prototyping, because you can get the voltage you need (such as 3.3V, 5V and 9V) as easy as that.
Note: Input must be >1.5V higher than output.