In 2009 each block minted 50 new BTC. Halvings in 2012, 2016, 2020, and 2024 stepped that down to today’s 3.125 BTC; ~2028 cuts it to 1.5625. The chain continues until the subsidy rounds to zero around 2140, at which point all 21 million coins exist.
Halvings are famous for preceding bull markets — supply growth halves overnight while demand persists. Whether that pattern is causation or coincidence-plus-narrative is eternally debated; the supply math itself is not.