Long story short:
Steemit was bought by Justin who implements his rules by bribing witnesses, and putting his own witness servers to run whatever HF he wants in case they don't agree. He mutes users, deletes posts and blocks accounts that he doesn't like.
Most people moved to Hive to stay away from that.

All your Steem history was mirrored to Hive, so you have all your old posts and wallet balance here. You simply continue what you started in a new place. Steem and Hive are separate blockchains now with separate tokens. You still have your Steem in Steem.