Bitcoin halving is often referred as "Halvening", it’s a formulated reduction in the reward coins offered to the miners using a predefined blockchain algorithm.
Bitcoin halvings take place once in every four – 4 years approximately, or for every 210,000 block transactions.
The process of halvening started in the year 2012, approximately after 4 years of invention of bitcoin i.e 2008, but practically bitcoins came into play in the year 2009.
After the first bitcoin halving, the block reward of 50 bitcoins per transaction were reduced to 25 bitcoins per block or transaction, later this reward was further reduced to 12.5 and will now fall to 6.25 after halvening in 2020.
The main idea of halvening is to create scarcity for the coins and to control inflation, as bitcoins issuance is limited to 21 million coins as per the idea of Satoshi Nakamoto, inventor of Bitcoin.
The production of 21 million bitcoins involves 32 halvenings, we are now done with two halvenings and this might continue till or come to an end in the year 2140.
To get the detailed information and for better understanding of Bitcoin Halving, checkout the following infographic