Explanation
The commands nc and telnet can be used to connect and interact with remote TCP network services. nc stands for netcat, a utility that can read and write data across network connections using TCP or UDP protocols.
telnet is a client-server protocol that allows a user to communicate with a remote host using a virtual terminal.
Both commands can be used to test the connectivity and functionality of network services such as web servers, mail servers, FTP servers, etc. by specifying the host name or IP address and the port number of the service.
References:
LPIC-2 exam 201 topics, section 205.1, "Use and configure network monitoring tools".
LPIC-2 exam 202 topics, section 208.1, "Implementing a web server".
Linux Essentials 010 exam objectives, section 4.3, "Basic network configuration and troubleshooting".