The Arduino USB Host Shield allows you to connect a USB device to your Arduino board. The Arduino USB Host Shield is based on the MAX3421E (datasheet), which is a USB peripheral/host controller containing the digital logic and analog circuitry necessary to implement a full-speed USB peripheral or a full-/low-speed host compliant with USB specification rev 2.0.
Technical Specification
Operating Voltage: 5V
USB Controller: MAX3421E
Maximum Current: 500mA when Arduino is powered by a suitable power supply connected to the Arduino
Maximum current: 400mA when Arduino is powered by its USB port.
Applications
It is used to connect a USB device to Arduino board.