The W04 is a standard bridge rectifier in a 4 pin compact package. You can use it to convert a AC voltage to a DC voltage. Being small and compact it takes less space than a standard 4 diode bridge rectifier.
It has a maximum voltage rating of 1000V and current rating of 1A. It has two input pins and two output pins. Just connect the AC source to the input pins and you will get a DC voltage at the output pins.
Use it to convert AC voltages to DC. Also, you can use this for reverse polarity protection for all your boards and projects.