Why is used auth_token to secure forms?

The attack from forms can be solved also using code like.

[code=php]
<div style=”margin:0;padding:0″><input name=”authenticity_token” type=”hidden” value=”9b7a4b5cb8f7c7910dsd797sdcnmxcox8c0df&#269;2582110887ff5″ /></div>

[/code]

Steps of security:
1. GET the form and token
2. then POST the form and token

How does the auth_token provide security if I use this sample?

Also in #PHP _↴