This list includes a bunch of different commands that are useful to know when working with Linux. Not all of these commands are covered in the videos, so feel free to investigate them on your own.
Managing files and directories
cd directory: changes the current working directory to the specified one
pwd: prints the current working directory
ls: lists the contents of the current directory
ls directory: lists the contents of the received directory
ls -l: lists the additional information for the contents of the directory
ls -a: lists all files, including those hidden
ls -la: applies both the -l and the -a flags
mkdir directory: creates the directory with the received name
rmdir directory: deletes the directory with the received name (if empty)
cp old_name new_name: copies old_name into new_name
mv old_name new_name: moves old_name into new_name
touch file_name: creates an empty file or updates the modified time if it exists
chmod modifiers files: changes the permissions for the files according to the provided modifiers; we've seen +x to make the file executable
chown user files: changes the owner of the files to the given user
chgrp group files: changes the group of the files to the given group
Operating with the content of files
cat file: shows the content of the file through standard output
wc file: counts the amount of characters, words, and lines in the given file; can also count the same values of whatever it receives via stdin
file file: prints the type of the given file, as recognized by the operating system
head file: shows the first 10 lines of the given file
tail file: shows the last 10 lines of the given file
less file: scrolls through the contents of the given file (press "q" to quit)
sort file: sorts the lines of the file alphabetically
cut -dseparator -ffields file: for each line in the given file, splits the line according to the given separator and prints the given fields (starting from 1)
Additional commands
echo "message": prints the message to standard output
date: prints the current date
who: prints the list of users currently logged into the computer
man command: shows the manual page of the given command; manual pages contain a lot of information explaining how to use each command (press "q" to quit)
uptime: shows how long the computer has been running
free: shows the amount of unused memory on the current system