Bitcoin is a crypto currency which is used as a means of exchange and also a store of value,  it is called crypto because it was built in a way that it cannot be copied this was done one the blockchain,  without the blockchain there can be no decentralization of bitcoin.  Blockchain is an open ledger where transactions are being stored,  all transaction stored are distributed and decentralized. Meaning that everyone has access to be information but no one owns the information. Bitcoin is a coin built on the blockchain,  while the blockchain is like a decentralized database with no owner.

What is shares in mining? Why getwork response doesn't solve the block directly and only one getwork response from many solves the block? Are they additive or something?