Port 23 is the telnet port, which allows remote access to a terminal.
Telnet is an old and unencrypted protocol: credentials and data are transmitted in clear text over the network.

It is possible to connect using a login/password.

$ telnet 10.0.0.11

After connecting, a username and password are usually required.

Due to the lack of encryption, using telnet is strongly discouraged on unsecured networks.
It is recommended to use SSH instead whenever possible.