Understanding how it works: "Post" deleting

It works! I just don't quite understand how Ruby understands the code.

I have a posts_controller.rb with a "destroy" method.
In the index.html.erb file, I have the link_to..

<td><%= link_to 'Destroy', post, :confirm => 'Are you sure?', :method
=> :delete %></td>

It states that the method is of symbol delete!
How does Ruby know that ":delete" is the "destroy" method?
i.e. At what point does delete translate to destroy?

I can't see how they're linked!