Halving is a event that happening every 4 year and causing for the block mining rewards to be half from 25 to 12.5 and it also result for increasing mining difficulty so the miners will spend more time to mine bitcoin.
Users gets profit on that even by buying bitcoins on a lower price and keep holding it and waiting for the price to rise just what expecting on halving. But i think that the expensive price that will happen on halving (july) will not last for a long time because many users will sell their coins also. So it will result for the price to be low again.