The Power Dock allows you to use any 3.7V LiPo battery to power your Omega and then charge the battery when it's out of juice. It has the same form factor as the Expansion Dock and can also be used in the same way: no battery and receiving power through the Micro USB port. The 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.
Note that the Power Dock does not have include USB-to-Serial chip, so you will need to use SSH or the Console over WiFi to connect to your Omega. See the links below on how to do this.
Note: Omega2 is NOT included.