The Anker Astro E4 is a battery pack. It's a battery that you can charge at home, and eventually use to charge your other USB based devices, such as mobile phones, tablets, and music players. The Astro E4 stores about 13000 mAh, which should be enough to charge a phone several times and might even be close to fully charging an iPad. More details and images below.
Back of the box. Just about every detail you need to know can be found here.
Box without the cover.
Inside of the box.
Box contents: several adapters (micro USB, mini USB, iPod 30-pin adapters), USB cable, Astro E4 unit, documents, and carrying pouch.
The Astro E4 on the side. The charge port is micro USB, the top has blue LED lights which show how much charge the device has, and the button activates the blue lights.
Two full-sized USB ports, one delivers 2A and the other 1A.