There's the steem blockchain and then a bunch of different ways to access it. You've probably using steemit.com there's also busy.org, zappl, dtube, dsound, dMania to name a few. Some of those different websites cater to slightly different content for different communities. But, all backed by the Steem blockchain.
Another thing steem can do is it has a zero fees wallet. Yep. Zero fees and transactions happen in a few seconds.