On the surface, it’s fairly similar to Slashdot, Metafilter, Reddit, or any other community site on the Internet.
The different thing about Aether is that it doesn’t have a server somewhere. The only thing the app does is that it finds and connects to other people using Aether. In other words, it’s a distributed, peer-to-peer network.
This makes it impossible to censor, and renders its users anonymous. It’s useful for people concerned about privacy, or pretty much anyone who doesn’t want to be watched and catalogued for every word they write on the Internet (so, pretty much everybody).
It’s also temporary. Whatever you post disappears after six months. It’s designed to be an ephemeral space, and it’s focused on now, rather than the past. Other people can still keep copies of what you wrote, but it won’t last forever in the network itself. They also won’t know who you are.