CAL: The code Cal in the system displays this month calendar.

CD:The code cd is used to help change or test the directory in the system.

DF: The code df is used to show the free space on mounted filesystem.

File: The code file is use to use to display the user information or to open additional folders in the system.

Free: The code free displays the  used and free memory that is avaliable.

Less: Displays a specific files on search.

LS: ls -a code help display the information about files and dirctories.

PWD: pwd show the path of current directory.