How do laser work?

The slowest laser printers produce about four pages per minute (ppm), and are relatively inexpensive. Printer speed can vary widely, however, and depends on many factors, including the graphic-intensity of the job being processed. The fastest models can print over 200 monochrome pages per minute (12,000 pages per hour). The fastest color laser printers can print over 100 pages per minute (6000 pages per hour). Very high-speed laser printers are used for mass mailings of personalized documents, such as credit card or utility bills, and are competing with photolithography in some commercial applications.