Not that this is necessary a bad thing. Laser and LED (Light Emitting Diode) printers have existed side-by-side for some years now, and in fact, most users aren't able to distinguish between the print quality of the two. For this reason (and to keep marketing the printers simple), most stores and sales Web sites will class LED printers as laser printers. There are, however, some differences between the two.
How They Work
Here's basically what happens when you print using a laser printer: The printer has a revolving cylinder (called a drum) that is given a positive electrical charge. When you send an image of a document or a picture to the printer from your computer, the printer uses a low level laser beam to "draw" the image on the drum using a negative electrical charge. This is called an electrostatic image. (In some printers, this works with the charges reversed -- that is, a positive electrostatic image on a negative background.)
As the drum continues to revolve, it passes the toner cartridge. The toner consists of fine black powder, which clings to the electrostatic image created by the laser on the drum. It then rolls over the paper, which has been given an even stronger electrostatic charge, and so the toner (still in its pattern) transfers to the paper.
The paper, which is now on its way out of the printer, first passes a fuser, heated rollers which melt the powered toner onto the paper. (The fuser is the reason, by the way, that you should be careful when opening up a recently used laser printer.)
LED printers work on the same principles. However, instead of a laser, an LED printer uses a group of LEDs built over the width of the drum, which are selectively beamed onto the drum in the form of tiny dots, or pixels.
Why Buy LED?
While you may not be able to tell the difference between LED and laser printers by simply looking at them, there are some things that distinguish them beyond their mechanics.
For example, LED printers tend to be less expensive than equivalent laser printers. This is because LED printers have less moving parts -- instead of a laser printing bouncing off a mirror and moving over the drum, you have stationary LEDs clicking on and off. For this reason, LED printers may also be longer-lasting than laser printers, although there are no statistics to prove this one way or the other. And there is some evidence that LED printers will work best and last longer if you are doing print jobs involving very high volumes of paper -- because the LEDs are clicking on and off with each job, the more they switch, the shorter their life span.
