It provides prototyping board space to build custom circuits and is great to build custom projects with the Arduino. All IO pins of the Arduino can be tapped into through header pins and empty solder pads for easy expansion.

It has a nice standard 0.1"x0.1" prototying grid with big pads

Comes with Stacking headers and plain header, choose whichever you want when soldering together

A IC pattern for adding DIP ICs up to 20 pins

Power rails down the middle and sides

A reset button and an extra general use button

2 3mm general use LEDs, red and green, as well as 2 matching resistors

A pass-thru ICSP stacking header so you can stack any kind of shield on top, and/or use an AVR programmer

A surface-mount chip area for up to 14 SOIC size parts

Compatible with tiny breadboards

Every pin is brought out!

Gold plated pads

2 x 0.1uF capacitors on either side for extra power stability