title: In an interface declaration, what do parentheses mean?
body: <p>An example:</p>
  
  <pre><code>interface IResourceService {
      (url: string, paramDefaults?: any,
          actions?: any, options?: IResourceOptions): IResourceClass&lt;IResource&lt;any&gt;&gt;;
  }
  </code></pre>
  
  <p>What does the syntax <code>(variable: type): Type;</code> mean? How can I implement this interface?</p>