title: ruby on rails, colon at back or front of variables
body: <p>I am new to ruby , and rails both. I think Rails is one of the best API, and ruby is quite unique, it seems that ruby can cleverly do "assumptions" to help developer. But I am not too sure to what extend.<br/><br/>
  my questions is about colon in variable. <br/>
  What i have understand so far is that <strong>:variable</strong> in ruby, is to say that this variable will not be able to change, which is similar to constant in other language. Am I correct?? </p>
  
  <p>Then my confusion is, sometimes i see the colon infront of variable, like this </p>
  
  <pre><code> Rails.application.config.session_store :cookie_store, 
        key: '_blog_session'
    &lt;%= link_to "Delete", article, confirm: "Are you sure?", 
        method: :delete %&gt;
  </code></pre>
  
  <p>Both <strong>key:</strong> and <strong>method:</strong> has colon in front.What does that this represent?
  and Furthermore</p>
  
  <pre><code>Blog::Application.routes.draw.do
    root :to =&gt; "articles#index"
  end
  </code></pre>
  
  <p>There are double colons inbetween variables?
  now I am guessing that Blog: is one variable, and :Application is constant. which i doubt it is, because it doesnt make sense. Please enlighten me? <br/><br/>thank you</p>