What are the differences between monitor and printer?

A monitor is the display for a computer system and includes the display device, circuitry, and enclosure. Most monitors today have an LCD (liquid crystal display) screen. A printer can be connected via USB cable or wirelessly to a computer in order to produce paper copies of what is displayed on your computer monitor. Printers are completely optional computer accessories, while monitors are more essential so you can see what's on your computer.