Every 210,000 Bitcoin blocks or approximately every 4 years, the number of new Bitcoins created every day gets cut in half. Called the Halvening—in Bitcoin jargon—the event is going to take place in less than 100 days. This event is what allows Bitcoin to maintain its supply cap at 21 million while also supplying the necessary rewards for miners for securing the network.
Currently, 1,800 Bitcoins are mined every day. This will be cut to 900 daily after this next halving event.
Though people argue that designing this event into the code is what has pushed Bitcoin prices to new highs, this event was built into the Bitcoin protocol by Satoshi Nakamoto.