The block reward is the incentive that motivates miners to add new blocks to the blockchain. This reward is given to the miner who successfully validates a new block, a process known as mining. The reward consists of a pre-determined number of coins, known as the coinbase transaction.
The block reward is the primary way that new coins are introduced into the circulation in proof-of-work blockchains. At pre-determined intervals, the number of coins awarded as the block reward is halved, an event known as a "halving".
This predictable creation of new coins at regular intervals ensures that the inflation of the coin supply is known, predictable, and cannot be manipulated.
Around the year 2140, the block reward will become almost negligible. When this happens, miners will have to rely on other sources of income, such as transaction fees, business sponsorships, altruism, investment, idealism, and so on.
* All terms and definitions may update as the Cryptionary improves.