This is a heavy duty step-down converter, which can efficiently convert up to 300W. You can control Constant Voltage (CV) and Constant Current (CC) with the two potentiometers on the left.
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.
The module is not isolated, and does not have reverse polarity protection, so make sure you put red to + and black to - !
You can use this for charging batteries, an LED driver, or most cases where a lower voltage is required than what you have available. We have used these to run long strips of 5V addressable LEDs off a 12V battery.