Inkjet printers are pretty complex machines. They were only introduced in the mid 1980's and revolutionized home and small business printing. How do inkjet cartridges and printers work, well, there are two main makes of inkjet printers; thermal bubble and the piezoelectric.
You may recognize the first as ‘bubblejet' printers. The ‘bubblejet' or thermal bubble, uses resistors which create heat. This heat literally creates a bubble in the ink. The bubble continues to expand until it forces the ink out from the inkjet cartridge head. The bubble soon collapses drawing more ink into the inkjet cartridge. With the piezoelectric model inkjet printer, there are small crystals in the head which will vibrate under the influence of an electric current.
The current then pushes ink out of the inkjet cartridge head and draws more ink into the cartridge. Image quality on these models is far superior because of the smaller drops of ink that are released from the head. Thermal bubble method is the standard for printer manufacturers. That is all except Epson who owns the patent piezoelectric technology. You will need different inkjet cartridges depending on which model you have, so double check before you go shopping.