Extremely short version: it's a hardfork of steem that a lot of people (including me) have shuffled off to. (I recommend using peakd as it works a lot better out of the box but you can use the condenser version at hive.blog if you like condenser/the steemit 90s look :))

_{but I'm commenting here now you ask? I'm keeping an eye on powerdowns and also checking up on any stragglers I follow that don't know what's going on or don't want to move for whatever reason so I'm still commenting but not going to be posting here anymore}

You may have to use steempeak or busy or a frontend that isn't steemit to find out the backstory as the new owners of steemit have been censoring posts (for their and everyone else's own good of course) if you really want to.