They enable network administrators to remotely access and manage a device. Telnet and SSH (Secure Shell) are two network protocols used to connect to remote servers in order to facilitate some sort of communications. Various Telnet clients and SSH clients running Telnet and SSH protocol can help access the Telnet server and SSH server to execute configuration and management remotely.
You could access a server in another place as easily as you could while you were sitting right at the keyboard by using Telnet and SSH.
