A fax, short for facsimile, is a method of sending documents over a telephone line. It works by scanning a physical document, converting it into a digital signal, and transmitting that signal to a receiving fax machine. The receiving machine then prints out a copy of the original document, allowing for quick and efficient communication. Fax machines were widely used in offices before the rise of email and digital communication. While their popularity has declined, they are still used in certain industries, such as healthcare and legal, where secure document transmission is essential. Many modern offices now use online fax services that allow sending and receiving faxes via the internet.