ls [-aAlgF] [filelist]
This command lists files in your current working directory or in another specified directory. Without any arguments it lists only non-hidden files (those w/o a leading dot '.'). The following options modify the output of ls:

-a List all files, including hidden files.
-A Like -a, but does not list dot '.' and dot-dot '..'.
-F Appends a slash '/' to directories, an asterix '*' to executable files, and an '@' is appended to symbolic links. Regular files have nothing appended.
-l Long listing format (one file on every line) with extra file information, in cluding: Type, file permissions, number of links (you'll never need to worry about this), owner, size, date it was last modified and the name of the file (symbolic links show up as `linkname -> path'). Here is the result of an ls -la:
total 16
drwxr-xr-x 2 ice 512 Mar 28 13:56 .
drwxr-xr-x 8 ice 512 Mar 23 11:09 ..
-rw-r--r-- 1 ice 13973 Mar 28 13:56 intro

-g Prints the group ownership of the file in a long listing. This option can only be used with the -l option. Thus: ls -lg
total 15
-rw-r--r-- 1 ice isu 15343 Mar 28 14:13 intro
You'll notice in the example above, the first string of characters (-rw-r--r--). This is called the 'mode' of the file. The first position denotes the type of the file. The valid types are:
d Directory
l Symbolic link
- Regular file
There are more types, such as block special files (b) and so on, but you really don't need to know what those are, unless you're the system administrator, and lets just say, that so far you're far too dangerous to be let anywhere near the root console!

The rest of the 'mode word' tells you about the file permissions that that particular file has. These last nine characters are divided up into three further fields, one for the owners permissions, one for the owners group, and one for everyone else. Thus:

  d   rwx   r-x   r-x
   \    \     \    `---	Everyone elses file permissions (read & execute)
    \    \     `-------	The group's file permissions (read & execute)
     \    `------------	The owner's file permissions (read, write & execute)
      `----------------	The type of the file (directory)
The 3 characters in each file permission field correspond to read, write and execute. If one of them is not set, it shows as a dash '-' in that particular field. On directories, the execute field does not mean that you can run the directory, it means that you can cd (change directory) into that directory and access files in it (thus, instead of called execute permission, it is called 'search' permission). However if the read permission is not set for a directory, even though one can cd into it, one cannot list the files in it. This is useful for letting people access known files in a directory, but not actually see what else might be there. We'll get into this more later.