Need explanation -> Passing 'id' in a form / link_to

Just need some more inside information…

Sample Code from the AWDWR book.

<%= link_to ( image_tag( product.image_url ),
{ :action => :add_to_cart, :id => product },
:method => :post,
:confirm => “Are you sure?” ) %>

Why is my :id => symbol using ‘product’ and not ‘’

Is the :id symbol ‘dual purpose’ and used as a key for an id param AND
it also infers that the FIELD to ‘get’ from the product object is named


Sorry, posted here by mistake… reposting to rails forum.