The coins awarded to a miner or group of miners for solving the cryptographic problem required to create a new block on a given blockchain.
Blockchains are sequences of individual blocks, each of which contains a record of transactions completed within a given period. Each block has an associated cryptographic hashing problem. This problem must be solved in order for the block to be created and added to the blockchain. Users of the blockchain are rewarded with cryptocurrency for solving these problems.
The process of solving hashing problems is known as mining. Most blocks on Bitcoin and other blockchains are created by groups of miners using specific mining equipment. In the case of Bitcoin, the asset was originally designed to be mined using conventional CPUs. But, as time went on, it became more efficient to use GPUs and, eventually, dedicated hardware known as ASICs.
On the Bitcoin blockchain, the original reward for solving a hashing problem was 50 BTC. However, this reward has been gradually reduced over time — falling by 50% every 210,000 blocks. This event is known as halving. At the current rate of discovery, a Bitcoin halving occurs around every four years. After 64 halvings, the reward will reach zero.
Block rewards are conferred on the relevant miner as the first transaction recorded in the given block. Bitcoin mining is now generally only viable as a profitable exercise for extremely large-scale mining operations, using expensive hardware in tightly controlled conditions and in locations with low energy costs.