Bitcoin is a System based on ownership not debt, no one can seize it no no one can censor it.
A Bitcoin, or cryptocurrency is simply a new way of transacting. It was invented by Satoshi Nakamoto (a pseudonym) as a peer-to-peer (P2P) electronic cash system and was first released in January 2009.
A block chain is a transaction database shared by all nodes participating in a system based on the Bitcoin protocol.
Bitcoin mining simplified.