Yet another VoIP client.
A clumsy "pretends to be pretty" interface, but it seems reasonable enough. Definitely not better than Mumble for the basics.
It might be better-suited for large groups, or because it has a free server, or some other thing I haven't discovered. I'll keep it in my toolbox, but I don't really like it.
Entertainment > Games + Internet >
A video broadcasting service. It's generally used for live-streaming gameplay.
The concept of twitch or other video streaming services confused me until I thought a bit more. See Why would live streaming be popular?