The Adafruit Feather are a complete line of development boards from Adafruit that are both standalone and stackable. They're able to be powered by LiPo batteries for on-the-go use or by their micro-USB plugs for stationary projects. Feathers are flexible, portable, and as light as their namesake.
We also carry a complete line of accessories and Feather Wings to stack boards and add room for prototyping. At its core, the Adafruit Feather is a complete ecosystem of products - and the best way to get your project flying.