A more thorough explanation:

Definition: Fax is a method of sending an exact copy of a printed document over telephone lines. It can also refer to the machine used for this transmission or the communication that is sent or received by the machine. Another term for fax is telecopier.

• She sent a fax of the contract to the client.
• The office has a fax machine for sending and receiving documents.
• He received a fax from his doctor with his test results.

These examples illustrate how fax is used to send and receive documents over telephone lines. In the first example, the sender used a fax machine to send a copy of a contract to the recipient. In the second example, the office has a fax machine for sending and receiving documents. In the third example, the recipient received a fax from their doctor with their test results.