When Bitcoin launched, miners would be awarded 50 BTC for each valid block they found.
The first halving took place on November 28th, 2012. At that point, the protocol reduced the block subsidy from 50 BTC to 25 BTC. The second halving occurred on July 9th, 2016 (25 BTC to 12.5 BTC). The last one took take place on May 11th, 2020, bringing the block subsidy down to 6.25 BTC.