There are several different types of printer ink cartridges. Most printer manufacturers make their own ink cartridges custom-made to fit the various models they manufacture. Therefore Canon cartridges will be different from HP Deskjet cartridges, even though the essential function is the same. How it Works Printer ink cartridges are basically replaceable sealed units that contain the specially processed ink a printer uses during its functioning. The cartridges typically contain one or more partitioned ink reservoirs.