The Blockchain means the Servers (computers) which store this website, but this website is saved on all of the Servers all at once, decentralized, like a Bitcoin network, and the system of that is locked and saved and copied on all the servers and my name is Oatmeal and what you comment, post, upvote, flag, resteem, is saved on the blockchain. Generally, blockchain networks, like Steemit, uses cryptography or at least Bitcoin does.