In practice
The halving cuts the rate at which new Bitcoin is created, so fewer new coins reach the market each day. It is written into Bitcoin's code and its approximate date is known years ahead; the most recent was in April 2024.
Long-term investors treat it as a milestone in Bitcoin's supply schedule, and the whole crypto market pays attention to the months around it.
What to watch for
There have been only a handful of halvings, far too few to prove a pattern, and an event known years in advance may already be reflected in the price. It is not a short-term trading signal.