Kez Darksun
Explorer
The Channel Divinity abilities are class features that work like powers, so you get those as well as your choice of an encounter power. The [w] indicates weapon damage. So, in your example if you were using a Long Sword, you would deal 1[1d8]+Cha modifier, or more simply read, 1d8+Cha modifier. If it said 4[w] it would be 4d8 for a Long Sword.