When you forget a command’s syntax or want to discover the right tool, Linux already includes several built-in help systems.
man
man command
Use man for the full manual page. Inside the viewer, press / to search, n for the next match, and q to quit.
–help and shell help
command --help help cd
--help is useful for a quick option summary. Bash built-ins such as cd are documented with the shell’s help command.
whatis and apropos
whatis tar apropos archive
whatis gives a short description of a known command. apropos searches manual-page descriptions and is useful when you know the task but not the command name.
These local tools are more reliable than old command-reference links because they match the software installed on your system.