Ruby on Rails : symbol as argument in form_for
Using the symbol will generate:
<form action="/users" method="post">
Using the object @user set to new you get:
<form action="/users" class="new_user" id="new_user" method="post">
If you set @user to something else it will change the form tag generated, of course ... try it out for yourself.
In the end it all depends what you're trying to do. You might want to use the symbol if you have multiple :user forms on the same page.