The command history often enables you to retrieve an earlier command that’s similar or identical to the one you want to enter. Tab completion reduces typing effort by letting the shell finish long command names or filenames. Command-line editing lets you edit a retrieved command or change a typo before committing the command.
The man command displays the manual page for the keyword (command, filename, system call, or other feature) that you type. This documentation provides succinct summary information that’s useful as a reference to learn about exact command options or features.