Bitcoin Halving is the phenomenon by which the miner reward keep on halving, or decrease by 50% after every four years, which happens after mining 210,000 blocks. Satoshi, the creator of Bitcoin wanted to create a system that would be self-sustaining, similar to gold mining. So, in order to control supply, he came up with the method of Bitcoin halving.
Video for basic explaining on- Bitcoin Halving 2020 | Bitcoin Halving Effect on Price | BTC Price Prediction 2020
https://www.youtube.com/watch?v=GNFMIXNW48I
Bitcoin Block Reward Halving countdown based on Average Daily Block Time
https://bravenewcoin.com/data-and-charts/bitcoin-halving
Previous Bitcoin Halving
Sources: https://coinswitch.co/news/bitcoin-halving-2020-bitcoin-halving-explained-read-more
https://bravenewcoin.com/data-and-charts/bitcoin-halving