POST and GET are methods of transferring form information to another page without using cookies, sessions, etc.
To use forms this way, you need a dynamic page that reads the information you're posting to, such as an ASP, PHP or CGI page.
Refer to this page with the action attribute:
Using GET will take all the values of the form inputs and put them in the querystring. For instance, using this code and typing "test" in the box it creates:
<form action='form_reading_page.php' method='get'>
<input type='text' name='textbox'/>
<input type='submit' value='go'/>
...will take you to the page
Using POST, the querystring is not created. So, using the same code as above, the information will be kept from visibility. This does not mean it is secure.
Getting values submitted from forms is very easy in the major server languages.
In PHP, POST values are retrieved like this:
$variable = $_POST['name_of_input'];
And GET like this:
$variable = $_GET['name_of_input'];
In ASP, POST:
When retrieving GET values, know that the user can manually add or change values just by typing the address in the page.
The method attribute is required for valid HTML, but most browsers default to GET without it.
Hope this clears things up a bit.