df is it displays the amount of disk space available on the filesystem containing each file name argument
cal displays the date so for instance here it shows September 17, 2014
free displays the amount of memory is being used and not used
cd means change directory allowing the program to change the current working directory in the operating system
pwd means what current working directory its on
ls shows command that lists directory contents of files and directories
file determines which file type it is on
less allows backward movement in the file as well as forward movement
