Ink cartridges are used in inkjet printers for computers. An ink cartridge is just that, a cartridge filled with ink. Most printers have two types of ink cartridges: black and color. The black ink cartridge usually has sport ween 10-20mL of black ink. The color ink cartridge has three different colors in the cartridge with a total volume of 10-20mL as well. The three colors in the color cartridge and the black cartridge allow for printing of color pictures. If you wish to print photograph quality pictures you have to change the black ink cartridge with a photo cartridge which will contain a lower amount of black ink as well as several more colors to allow for more vibrant and colorful pictures.
Ink cartridge prices have become a bit of a concern for many people. It's suspected that most printer companies sell the printer at cost or at a small loss to entice buyers, but then charge huge markups on ink cartridges to recover losses on the printers. This has lead to people attempting to refill ink cartridges themselves, or using third-party ink cartridges. Large printer manufacturers have begun suing these startup companies selling cheap ink cartridges saying they are infringing on their copyright ink cartridge designs. We'll have to wait and see how this turns out.