Each 'block’ on the blockchain contains a list of transactional data. This transactional data must be verified and secured to be added to the blockchain, at which point it can no longer be altered. This is done by 'miners'.
To verify transactions, miners have to solve complex mathematical problems. These require a tremendous amount of computing power to solve, as well as equipment, space, insurance, and so forth.
Miners, therefore, receive a block reward for each block of transactions they successfully mine and add to the blockchain. This reward is an incentive for Bitcoin miners to keep solving the mathematical problems and compensates them for their costs and time.
A rule in the Bitcoin software states that every 210,000 blocks, the block reward is halved – also known as the Bitcoin halving.
Currently, the number of Bitcoin generated as a reward for each new block added to the blockchain is 12.5 Bitcoin. The next block reward halving event is expected to take place in May 2020.
This is viewed as a significant event since the supply of new Bitcoin is reduced by 50%! (MISSING)This is because there will only ever be 21 million Bitcoin created. If the coins are created too quickly, the law of supply and demand dictates that there would be too many in circulation and they would have very little value.