The Power Dock 2 allows you to use any 3.7V LiPo battery to power your Omega and then charge the battery when it's out of juice. Utilizing the same form factor as the Expansion Dock, this board also can be used in the same way, so if you don't have a battery connected you will still be able to receive power through the microUSB port.
The Power Dock breaks out the Omega's GPIO pins so you can use them to control external circuits or connect expansion boards to extend the functionality of your Omega. The Power Dock 2 adds an ADC that allows the Omega to measure the voltage level of an attached LiPo battery. This will give you a better idea of how much juice is left in the battery!
The Onion Omega boards we carry are separated into three different categories: Mainboard, Dock and Expansion Board. This board falls into the Dock category, meaning you can plug an Onion Omega directly into the board. The Expansion Dock is also compatible with Omega Expansion Boards, making it one of the most straightforward docks produced by Onion.