Since processors were extremely expensive at the time, there were purely displaying, non-intelligent terminals called dumb terminals that could only send, receive, and display single characters. Later there were intelligent terminals, Smart Terminals, which had their own processor and could calculate simple text operations and text displays. For example, flashing characters or writing in a bold grade.
If one assigns the terminals to today's technology, then they form the clients in the client- server architecture. The dumb terminals correspond conceptually to the thin clients and the smart terminals to the fat or smart clients. However, a functional comparison is not appropriate because of the powerful processors in clients.