Let see with the example to understand clearly: input.html
<form action="testing.php" method="post">
Enter your message: <input type="text" name="msg" size="30">
<input type="submit" value="Send">
// retrieve form data
$input = $_POST['msg'];
// use it
echo "You said (POST): <i>$input</i>";
//you should change the method in html to "get"
$input1 = $_GET['msg'];
echo "<br/>You said (GET) : <i>$input1</i>";
Post will transfer your elements values to other pages you want. Samething happen with Get, but it will transfer the elements thru url query string.
In the above example when sending with post check ur URL (nothing added) when sending with GET you can see the differnce in URL.
Both the purposes are same to transfer values from one page to other.
A word on usage:
You should use $_POST for submitting forms, and $_GET when you need to redirect someone to a site an provide specific variable-value pairs. For example, if you have an e-commerce site, and your page loads product information from a database based on product ID numbers, you could have a link like: