What is Block Reward?

[Kakashi2020]

With as many as 300,000 purchases and sales occurring in a single day, verifying each of those transactions can be a lot of work for miners.  As compensation for their efforts, miners are awarded bitcoin whenever they add a new block of transactions to the blockchain.

The amount of new bitcoin released with each mined block is called the "block reward." The block reward is halved every 210,000 blocks (or roughly every 4 years). In 2009, it was 50. In 2013, it was 25, in 2018 it was 12.5, and in May of 2020, it was halved to 6.25.

 Bitcoin successfully halved its mining reward—from 12.5 to 6.25—for the third tme on May 11th, 2020.
This system will continue until around 2140.  At that point, miners will be rewarded with fees for processing transactions that network users will pay. These fees ensure that miners still have the incentive to mine and keep the network going. The idea is that competition for these fees will cause them to remain low after halvings are finished.

These halvings reduce the rate at which new coins are created and, thus, lower the available supply. This can cause some implications for investors, as other assets with low supply—like gold—can have high demand and push prices higher. At this rate of halving, the total number of bitcoin in circulation will reach a limit of 21 million, making the currency entirely finite and potentially more valuable over time.