Answer Description
After a printer applies toner to paper the fuser assembly rolls over the paper and applies heat to fuse the toner to the paper. Occasionally, the toner can stick to the fuser assembly and will be applied to the next sheet of paper passed through the printer.
Wikipedia
Laser printing is an electrostatic digital printing process. It produces high-quality text and graphics (and moderate-quality photographs) by repeatedly passing a laser beam back and forth over a negatively charged cylinder called a "drum" to define a differentially charged image. The drum then selectively collects electrically charged powdered ink (toner), and transfers the image to paper, which is then heated in order to permanently fuse the text and/or imagery. As with digital photocopiers, laser printers …
Laser printing - Wikipedia, the free encyclopedia