Ink Jet Printers
Ink jet cartridges contains liquid ink that is sprayed onto the page with thousands of ink droplets per second. Inkjet cartridges can have up to 600 nozzles. The ink droplets are very small, approximately 50 - 60 microns in diameter. To the everyday person this translates as thinner than a single human hair. The drops of colours combine to form any colour needed which is why ink jets can produce picture perfect photos.
The two main inkjet printers are bubble jet and pierxoelectric
Bubble Jet (which were developed by Canon and HP). An electric current is used to heat up a small metal component in the ink cartridge. As it heats up a bubble is formed causing the ink to push out through the nozzle onto the paper.
Pierxoelectric (developed by Epson) and uses piezo crystals in the ink jet cartridge. An electric current makes the crystals vibrate, expand and force ink out of the nozzle.
Laser Toner Printers
In contrast laser printers use laser toner cartridges which hold dry ink. Static electricity and heat is used to print on the pages. It is not really ink but electrically charged particles. The laser printer has a drum unit, heat roller and pressure roller besides the laser toner cartridge and they all contribute to the printing process. Put simply, it sticks the toner to the paper. The drum unit rolls charging itself positive, then a laser beam throws a light onto the surface of the drum. While it rotates an electrostatic image is created, toner particles are charged and attached to the electrostatic image on the drum. Meanwhile the paper is passed through the drum, gets charged negatively causing the toner to stick and the image is fixed by the heat and pressure roller. Simple!