What is /dev/null?

I've used /dev/null for two purposes -
1. to discard output of a command
2. to suppress any potential error messages from a command

You may already know that you can redirect the output to a
1. file using greater than symbol ">" and 
2. command using pipe symbol "|"

Redirection to /dev/null works just as if the redirection was to a file. The only exception that the output cannot be retrieved.

Before we dive in, it's important to know that standard output is represented as 1 and standard error as 2.

ls -1 c* 2> /dev/null  #redirects the standard error (2)
ls -1 c* &> /dev/null  #redirects both the stderr (2) and stdout(1)
                              #variations include 2>&1, >>
ls -1 c* 1> /dev/null  #redirects the std output (1)
                          #variation is >

Here's an example to show an application of /dev/null. Run the code below to see how differently they behave.

if test ! -z "`ls -1 y* 2> /dev/null`"  ; then
   echo "Files starting with y exist."
else
   echo "Files starting with y DO NOT exist."
fi

if test ! -z "`ls -1 x* `"  ; then
   echo "Files starting with x exist."
else
   echo "Files starting with x DO NOT exist."
fi

To think about -
1. What happens when you do > filename?
2. What happens with you do > instead of 1> in the first example?
3. What does  this do? ls -1 c* 2> logfile > file.lst