A command language is a language for providing commands to computers and peripherals. Typical examples include DOS and PowerShell commands that you can use at the command prompt, shell scripts with SSH connections to servers, and so on.
For peripheral devices, the manufacturer's own command language is implemented.
Matsusada Precision's equipment implements original and SCPI command languages.
Previously, commands could be sent, received, and controlled using HyperTerminal, which included Windows.