There are three principal types of printers.

Dot-matrix printer: this old-fashioned and by now obsolete printer is noisy and slow and produces low-quality printouts. The dot-matrix printing head impacts an inked ribbon, like those used by the old typewriters.

Laser printers. Laser printer technology derives from photocopiers. A very narrow laser beam is directed against a drum made of photoconductive metal like selenium and modifies its electrical charge wherever it hits. The drum then passes through a powdered substance that attaches only to the areas of the surface that have been electrically charged.
A roller presses the sheet of paper against the drum and the powder is transferred to the paper. Next, the paper passes between two hot rollers that melt the powder, which then solidifies. Like in the case of the dot-matrix impact printer, the printed characters are composed of tiny points in the positions hit by the laser beam. Since the beam is very narrow, the points are almost invisible and the resultant quality is very high; furthermore, the fused powder technique produces a deep black, permanent printout. Despite the fact that the price is still quite high, this type of printer is very widely used because it produces a printout comparable in quality to professional printshop work.

Ink-jet printers. This type of printer has recently been much improved, with a considerable reduction in size and price and higher print quality. It has also made color printing economical and very faithful to the original.
As it passes over the sheet of paper, the printing head sprays thin streams of ink from a row of nozzles. Wherever the stream hits a point is formed; a set of points forms a character. This too is a "dot matrix" system, like in the impact printers, but since what "impacts" the paper is streams of ink instead of steel rods against a ribbon, the dots can be very closely positioned and even partially overlapping.
As the technology evolved, the drops of ink have become smaller and more precise. The result is characters made up of tiny dots that are almost invisible to the naked eye, and therefore a particularly clear printout. The only negative aspect with this type of printer is the speed, which is only moderate.

There are also printers for professional printshop use, like the dye-sublimation or thermal-wax printers for very high-quality reproduction.

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