The small set that covers most of what you do.
MOVING AROUND
pwd shows where you are ls lists files, with -l for detail and -a to include hidden ones cd changes directory
FILES
cat displays a file less pages through a long file, q to quit tail shows the end, with -f to follow a log live head shows the beginning cp copies, mv moves or renames, rm deletes
rm has no undo. Be deliberate, particularly with -r.
FINDING THINGS
find searches for files by name or attribute grep searches inside files for text which shows where a command lives
SYSTEM
top or htop shows running processes and resource use df shows disk space, du shows directory sizes free shows memory systemctl controls services
PERMISSIONS
chmod changes permissions, chown changes ownership
GETTING HELP
man followed by a command shows its manual. Most commands also accept --help.
