Yes they are all connected to steem and run on steem, just as steemit.com does and yes they all share the reward pool but soon there will be seperate content spheres once all the testing is done and Steemit Inc finished up work on Steem namespaces which is code for 'your own steem content on its own website, without other steemit content interfering' or to put it simply, Zappl content shows on Zappl only..