FOUNTAIN PEN

A fountain pen is a pen that contains a reservoir of water-based liquid ink. If it uses ink cartridges instead of having a built-in ink reservoir, it is often called cartridge pen. From the reservoir or the ink cartridge, the ink is drawn through a feed to the nib and then to the paper via a combination of gravity and capillary action, so most fountain pens require no pressure to write.
Filling the built-in reservoir with ink usually involves operating an internal mechanism which sucks ink from a bottle through the nib into the reservoir. These mechanisms are typically pistons or rubber sacs. Cartridge pens are filled by simply replacing the empty ink cartridge with a new factory-filled one.