help [command [subcommand]|expression]

Without argument, print the list of available debugger commands.

When an argument is given, it is first checked to see if it is command name. help backtrace gives help on the backtrace debugger command.

If the environment variable $PAGER is defined, the file is piped through that command. You will notice this only for long help output.

Some commands like info, set, and show can accept an additional subcommand to give help just about that particular subcommand. For example help info line gives help about the info line command.