Mining

Mining is the process by which new blocks are added to the Bitcoin chain and new BTC enters circulation. It's a continuous global race: every miner builds a candidate block from mempool transactions, then hashes its header with different nonces until they find one whose double-SHA-256 falls below the current difficulty target.

Whoever wins the race gets two things:

• The block subsidy - currently 3.125 BTC of newly issued Bitcoin.
• The transaction fees from every transaction they packed into the block.

That total payout - the block reward - is what pays for the electricity and hardware. There is no other meaningful revenue source. There is no other meaningful incentive to mine.

The global hash rate is currently around 700 exahashes per second (7 × 10^20 hashes per second). Every Bitcoin block represents about 10 minutes of every miner on Earth hashing simultaneously - roughly 4 × 10^23 attempts per block. That energy, by design, is what makes the chain expensive to rewrite. To reverse a recent block, an attacker would need to mine a longer fork - faster than the entire rest of the world is mining the real one. The deeper a transaction sits, the less plausible reversing it becomes.

Mining is sometimes described as "Bitcoin's energy problem." It is more accurately Bitcoin's security model. The energy spent buys the immutability of every transaction in the entire history of the chain. See the Mining rabbit hole for the long version.