Placing Stones on the Grave or Monument
As opposed to the common practice of burying loved ones with and placing loose flowers or other items by the tombstone, Jewish tradition instead puts an emphasis on placing stones on graves. This is not to be confused with the planting of flowers on the gravesite.
The origin of the stone custom is uncertain, though it may relate to ancient times when a pile of stones was used as a marker. The most common explanation is that placing stones is a symbolic act that indicates someone has come to visit and the deceased has not been forgotten.
The underlying theme is that stones last for eternity. Like the memory our loved ones, stones will never die.