Technically it's much more than Twitter - it's a way to subscribe to activities in realtime (Activity Streams + Pubsubhubbub), a way to easily do so for users on a website (WebFinger) and a way to notify people of others activities which they are being part of (Salmon).
The activity can be small status messages like Twitter - but can also be anything else, like photos, check-ins, whatever. So in that way it's much more like a distributed Facebook than a distributed Twitter - but right now the existing clients out there don't really show that very clearly.
The activity can be small status messages like Twitter - but can also be anything else, like photos, check-ins, whatever. So in that way it's much more like a distributed Facebook than a distributed Twitter - but right now the existing clients out there don't really show that very clearly.