Well to the best of my knowledge, Steem is the blockchain while Steemit(steemit.com) is just a front end website like any other websit,e that pulls its content from the Steem blockchain.

So Steemit, busy.org, steemd.com etc are all just “normal” websites that display content of the Steem blockchain but in different ways. They’re all connected to the same source.

So while Steemit.com was down, you could still access Steem via busy.org but it was loading way too slow.