72
At a high level, a Bitcoin halving is when the introduction of new bitcoins into circulation is reduced by half. This happens roughly every four years, and this schedule will continue until the last bitcoin is mined sometime around 2140. The supply is capped at 21 million BTC. This mechanism was devised by Bitcoin’s creator(s) as a way to enforce scarcity and deflationary properties of bitcoin. The idea is that, so long as the adoption of the Bitcoin network grows over time, a mechanism like this will ensure that the laws of supply and demand will consistently increase the value of the asset. In this sense, the monetary policy of Bitcoin can be viewed as having been designed to be a counterweight or alternative to fiat money, which historically devalues over time. That is, what you can buy with a U.S. dollar today is a lot less than what you could buy with a dollar 100 years ago.