A telegram is a message transmitted by telegraph. A telegraph is a device for transmitting and receiving messages over long distances, i. e. , for telegraphy. The word telegraph alone now generally refers to an electrical telegraph.
(n.) Electrical apparatus or process for sending a message (tel·e·gram)
(v.) To send by telegraph
1 Additional Answer
A telegram is a communication that is sent over a telegraph. A telegraph operator receives the communication then writes it out to the recipient. Telegrams can also be transmitted over the phone but are not so popular.