This is a high quality switching 'wall wart' AC to DC 5V 2000mA Barrel Jack wall power supply manufactured specifically for SparkFun Electronics. These are switch mode power supplies which mean the output is regulated to 5V and the capable output current is much higher (2000mA).
These wall adapters are perfect for supplying power to many single-board computers like the pcDuino, Beaglebone Black, or the Raspberry Pi. Please note, this specific supply (5V/2A) is also FCC/CE certified and works with 100-240VAC inputs and has a Center-positive 5.5x2.1mm barrel connector.
Note: These wall adapter power supplies may only output 4.5V when pulling a full 2A. Please keep this in mind when making your purchase.