Unix

cd
changes directory, by itself it will take you back to your home directory, and in conjunction with a directory name it will change to that directory.

ls
this command shows the files that are in a directory. this command can be modified by "-a", "-l" or both, -a shows you all the "dot" files in a directory and the -l shows your permissions.

whoami
this command shows you your current user name

exit
this command logs you off of the system