Every Bitcoin block value consists of the block reward (new coins issued) and the fees from transactions contained in the block. The block reward is hard coded for each block and, in the case of Bitcoin, its value is halved at intervals of 210 000 blocks (approximately once every four years).

When Bitcoin was created in 2009, the initial reward was 50 BTC per block mined. After the latest halving that happened on May 11, 2020 the mining reward is 6.25 BTC and it is going to be cut in half to 3.125 BTC in the spring of 2024 (see countdown). The halving process will continue until the final supply of coins - slightly less than 21 million - is reached.

Halving vs halvening. Which is correct?

Both terms refer to the same event. The proper name for the event is the halving but the community sometimes uses the word halvening instead (as a nickname) which was created by a merger of “to halve” and “to happen” — the halving which is happening is the halvening.