Every Command Has a Manual
Forgot what a command does? Can't remember the flags? There's a built-in manual for almost every command.
The man Command
man (short for "manual") shows documentation for any command:
Open the manual for ls:
man ls
Use ↑ / ↓ or Space to scroll
Press q to quit
Try a Few
Look up any command you've learned:
Learn all the options for copying files
Understand the dangers and safety flags
See all the formatting options
Quick Help With --help
Many commands also support --help for a shorter summary:
ls --help
This is less detailed than man but often enough to jog your memory.
Key Takeaway
man commandname opens the full manual. Press q to exit. For a quick summary, try commandname --help.