get you work on url
Ex:
www.dbforums.com/id=30
in php for get value in url $_GET['id']

<?php
$id = $_GET['id'];
echo 'Id is: ' . $id;
?>

Result is :

Id is: 30

in post you send a value of input in a form for the page in the action

<form method="Post" action="post.php">
<input type="text" name="text_post">
<input type="submit" name="Send">
</form>

"post.php"

<?php
$post_value = $_POST['text_post'];
echo "Post = " . $post_value;
?>

Result is:

Post = 'Value of Input text'