This term is related primarily to Travertine, which is characterised by surface pits and holes. These holes can be pre-filled at source by a stone resin which is as similar as possible to the colour of the stone. Once filled the stone is then worked to a Honed or Polished finish. Not every single pit/hole will be completely filled, and therefore even a pre-filled Travertine may require some filling by grout during the fixing process. It is not unusual for any natural stone tile to have some degree of surface fill present. Ongoing resin filling may be required as part of your maintenance regime.