/sbin/usermod     -  modify a user account
which            - shows path of the command you are using
date             - shows the date and can format it with the options
file             - shows what kind of file it is
head             - print top of file
tail             - print bottom of a file
cat              - print the whole file 
mkdir           - create a directory
rmdir           - remove a dir
pwd             - list your current working directory
cd              - no args - takes me home
cd -            - takes you to your last directory
cd ..           -  go back one directory
cd .            - go to this current directory
ls -a           - list hidden files
ls -l           - ls long listing
ls -laF         - long hidden and type
cp     - copy a file
mv     - move a file
rm         - remove file
mkdir       - make a directory
mkdir -p   - make a dir 

touch    - create an empty file