This is a USB Type A DC-DC step up power supply/converter module.  This is an ideal module if you need to provide a stable power source to a usb device.  This module will take a lower voltage between 0.9VDC and 5VDC and step it up to a stable 5VDC, available via the USB socket.  If you want to add a USB power port to your project, workspace, vehicle, etc. this is the perfect module to get the job done!