This is one of five possible methods for curing olives with. Curing olives draws out their bitterness. It is the first step in readying them to be used for Table Olives.
Olives are soaked in fresh water (e.g. no salt added, as is done for Brine-Cured Olives) for a month. The water is changed daily. This method is used mostly in the south of France. It doesn’t change the taste of the olive as much as other methods such as brining them will do, but the olives won’t store as well and for as long afterwards.