ls shows files and directories in present working directory. (if no arguments are passed.) (It doesn't show hidden files which starts with . by default.)
user@ubuntu14:/usr$ ls
bin games include lib lib32 local sbin share src
To see all files (hidden files/folders also).
Use ls -a OR l...
Full list of options:
ls -a list all files including hidden file starting with '.'
ls --color colored list [=always/never/auto]
ls -d list directories - with ' */'
ls -F add one char of */=>@| to enteries
ls -i list file's inode index number
ls -l list with long form...
