From Teletype to Terminal Window: The 3 Eras of Unix Terminals
The first computer terminals for interactive use didn't have screens. They were called teleprinters, or used the brand name Teletype. They were effectively automatic typewriters that could print text received from a remote phone line. They were already widely used for telegraphy because operators didn't have to know Morse code—they could use their fingers instead.
Because printing terminals were already widely used in telegraphy, they were applied to interactive computing when time-sharing operating systems were developed. Instead of punching cards and handing them off to a mainframe computer operator, and then waiting to get your output back, you could type in commands and run programs while getting immediate feedback.
There were a couple of downsides to this kind of terminal. Printing terminals needed to print, and they needed to print on paper. Second, they were slow. This was annoying if you wanted to type commands into a computer, one that could be many miles away.