A fax machine is a device that transmits scanned documents over a telephone line. It converts the document into a digital signal, which is then sent to another fax machine that decodes the signal back into a printed copy. This technology allows for quick and efficient sharing of information, especially in business settings. Although less common today due to digital communication methods like email, fax machines are still used in various industries, including healthcare and legal fields, where signed documents are often required. They provide a reliable way to send important documents securely and quickly.