Unix commands

cat Reading and printing multiple file
cd Changing directories, moving around
chmod Changing permissions of a file or directory
cp Copying files
date Displaying and setting dates
diff Differences between files
exit Stopping a process and coming back home
find Searching for files that meet specified conditions
finger Gathering information about users
grep Serching for lines that match regular expressions
head Printing the beginning of a file
kill Terminating process
less Displaying files
lprm Removing printer queue requests
ls Listing files
man Using the online manual
mkdir Making directories
more Displaying files
mv Moving and renaming files
passwd Creating or changing passwords
ps Active processes
pwd Printing the pathname
rlogin Logging into remote systems
rm Removing files and directories
rmdir Removing directories
su Logging in as another user
tail Printing the end of a file
telnet Communicating with other hosts
who Displaying information about a system

To access the on-line manuals ,use the man command,followed by the command you need help with.
man ls
to see the manual page for the "ls" command.