This is a good reference article. Also this.

Basics

Print stuff

echo "hello world!"

FS navigation

pwd
cd 
cd ..
ls
ls -a

FS manipulation

mkdir 
rmdir 

touch 
rm 
rm -rf 

cp source destination
mv source destination

chmod
chown

cmp
diff

Reading data from file

head hello.txt
tail hello.txt
cat hello.txt

grep

Open files in default editors

code file_name
edit file_name

OS and networking

ps 
kill -9 pid

uname
whoami

sudo

Helpers

clear
exit

man command_name
whereis
whatis
--help

ctrl+c
ctrl+shift+c
ctrl+shift+v
ctrl+alt+t
tab

alias

tar
zip
wget

Git commands

git init
git add .
git commit -m "commit msg"
git status

git clone
git remote add origin origin_url
git remote -v
git log

git pull
git push
git branch
git checkout
git merge

git diff