To get additional help on any of the commands listed below, you can always use the man command to get additional help.
man - accesses the online man pages
ls - lists the contents of a directory.
pwd - prints the current working directory
cd - changes directories
mkdir - creates a directory
rmdir - removes a directory (assuming it is empty)
touch - creates an empty file with the specified name or if the file already exists it modifies the timestamp
rm - removes a file. Can also be used to remove a directory and its contents.
mv - moves a file or renames a file, thus removing the original
cp - copies a file, leaving the original intact
cat - shows the contents of a file, all at once
more - shows the contents of a file, screen by screen
less - also shows the contents of a file, screen by screen
head - used to show so many lines form the top of a file
tail - used to show so many lines form the bottom of a file
date - shows the date and time on the current system
cal - displays a calandar
lpr - prints a file
lpq - show the contents of a print queue
lprm - remove a job from the print queue
who - used to print out a list of users on the current system