Requiring a proof of work to accept a new block to the blockchain was Satoshi Nakamoto's key innovation. The mining process involves identifying a block that, when hashed twice with SHA-256, yields a number smaller than the given difficulty target. While the average work required increases in inverse proportion to the difficulty target, a hash can always be verified by executing a single round of double SHA-256.
Bitcoin 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.
That’s why mining pools came into existence. The idea is simple: miners group together to form a “pool” (i.e., combine their mining power to compete more effectively). Once the pool manages to win the competition, the reward is spread out between the pool members depending on how much mining power each of them contributed. This way, even small miners can join the mining game and have a chance of earning Bitcoin (though they get only a part of the reward).
Paint mixing is a good way to think about the one-way nature of hash functions, but it doesn’t capture their unpredictability. If you substitute light pink paint for regular pink paint in the example above, the result is still going to be pretty much the same purple, just a little lighter. But with hashes, a slight variation in the input results in a completely different output:

As specified by the Bitcoin protocol, each miner is rewarded by each block mined.  Currently, that reward is 12.5 new Bitcoins for each block mined. The Bitcoin block mining reward halves every 210,000 blocks, when the coin reward will decrease from 12.5 to 6.25 coins.  Currently, the total number of Bitcoins left to be mined amounts to 4,293,388. This means that 16,706,613 Bitcoins are in circulation, and that the total number of blocks available until mining reward is halved is 133,471 blocks till 11:58:04 12th Jun, 2020 When the mining reward will be halved.
The blocks chain is secured by the miners. Miners secure the block by creating a hash that is created from the transactions in the block. This cryptographic hash is then added to the block. The next block of transactions will look to the previous block’s hash to verify it is legitimate. Then the miner will attempt to create a new block that contains current transactions and new hash before any other miner does.
In the zero-sum game that cryptocurrency has become, one man’s free money is another man’s headache. In the Mid-Columbia Basin, the latter category includes John Stoll, who oversees Chelan County Public Utility District’s maintenance crews. Stoll regards people like Benny as “rogue operators,” the utility’s term for small players who mine without getting proper permits and equipment upgrades, and whose numbers have soared in the past 12 months. Though only a fraction of the size of their commercial peers, these operators can still overwhelm residential electric grids. In extreme cases, insulation can melt off wires. Transformers will overheat. In one instance last year, the utility says, a miner overloaded a transformer and caused a brush fire.
Here’s how it works: Say Alice wants to transfer one bitcoin to Bob. First Bob sets up a digital address for Alice to send the money to, along with a key allowing him to access the money once it’s there. It works sort-of like an email account and password, except that Bob sets up a new address and key for every incoming transaction (he doesn’t have to do this, but it’s highly recommended).

That opportunity may not last. Huffman, who is also a former utility executive, argues that ever-cheaper power rates in other states, like California, could undercut the basin’s appeal to blockchain miners, who may begin to look for other places to mine. For that reason, Huffman argues that the basin should be actively recruiting more miners, even if it means importing power. “I think there’s a window here,” Huffman says, “and it’s unknown how long that window will be open.” Yet he, too, knows that any such talk will lead to criticism that the basin is yoking its future to a volatile sector that, for many, remains a chimera. “Some folks think that bitcoin is just a scam,” Huffman concedes. “And in the conversation, you usually don’t get past that.”
Bitcoin prices were negatively affected by several hacks or thefts from cryptocurrency exchanges, including thefts from Coincheck in January 2018, Coinrail and Bithumb in June, and Bancor in July. For the first six months of 2018, $761 million worth of cryptocurrencies was reported stolen from exchanges.[60] Bitcoin's price was affected even though other cryptocurrencies were stolen at Coinrail and Bancor, as investors worried about the security of cryptocurrency exchanges.[61][62][63]