Mining

• Mining is the process of adding transaction records to Bitcoin's public ledger of past transactions. This ledger of past transactions is called the blockchain as it is a chain of blocks. The block chain serves to confirm transactions to the rest of the network as having taken place. Bitcoin nodes use the blockchain to distinguish legitimate Bitcoin transactions from attempts to re-spend coins that have already been spent elsewhere.
• Mining is intentionally designed to be resource-intensive and difficult so that the number of blocks found each day by miners remains steady. Individual blocks must contain a proof of work to be considered valid. This proof of work is verified by other Bitcoin nodes each time they receive a block. Bitcoin uses the hashcash proof-of-work function.
• The primary purpose of mining is to allow Bitcoin nodes to reach a secure, tamper-resistant consensus. Mining is also the mechanism used to introduce Bitcoins into the system: Miners are paid any transaction fees as well as a "subsidy" of newly created coins. This both serves the purpose of disseminating new coins in a decentralised manner as well as motivating people to provide security for the system.
• Bitcoin mining is so called because it resembles the mining of other commodities: it requires exertion and it slowly makes new currency available at a rate that resembles the rate at which commodities like gold are mined from the ground.
• This is essentially what Bitcoin mining is, just rehashing the block header, over, and over, and over, and over, until one miner in the network eventually produces a valid hash. When he does, he relays the block to the rest of the network. All other miners check his work and make sure it’s valid. If so, they add the block to their local copy of the block chain and move on to finding the next block.