If you buy a new printer for your home, you will find the following feature in the technical data for some devices: Duplex unit. If you are not familiar with the hardware, ask yourself the following question: What is a duplex unit? The answer to this question can be found here in this article:
Multifunctional printers can print on both the front and back of paper. This two-sided printing process requires a unit that automatically turns the paper to be printed. This unit is called a duplex unit. This means that it is only possible to print automatically on both sides by means of a duplex unit.
If you want to have this procedure on a new printer to save paper, you should make sure that the printer has a duplex unit. Now you know why you need a duplex unit for a printer.