pio:tldr:b6289

This command is using the command-line interface (CLI) tool called "pio" and using it to execute a specific subcommand. The ${subcommand} placeholder is meant to be replaced with the actual subcommand you want to run.

The --help flag is a common convention in command-line interfaces that is used to display help information about a specific command or subcommand. By including --help, the command will show the available options, arguments, and usually a brief description of how to use the specified subcommand.

For example, if you replace ${subcommand} with train, the command pio train --help will display information about the "train" subcommand, explaining how it works and what options or arguments you can use with it.