Telnet is remote protocol which is used to remote though network media. Telnet is clear text remote management protocol by sending clear text username and password through the network. It is easy for hacker to capture data and explore the username and password. Telnet is unsecured remote protocol. Telnet use TCP port 23. We can telnet by command prompt, Putty, SecureCRT,… .
SSH is remote protocol which is used to remote thought network media as telnet too, but it is secure than telnet. SSH encrypt password before sending remote device through the network. SSH use TCP port 22.