Every 210,000 blocks (roughly a 4 year time period), a pre-determined reduction in issuance occurs, reducing the newly minted BTC coins by 50%. The fourth Bitcoin Halving took place over the weekend, seeing the block subsidy decline from 6.25BTC to 3.125BTC per block, or an approximate issuance of 450 BTC per day (for 144 blocks mined).

With every Halving, we can see some strong bullrun, so you know in longer vision what comes next.