title: Symfony: Relation between Bundles and Services
body: <p>I'm planning to write an AJAX extension for the forms in Symfony3. I want to be able to use ajax requests in many forms instead of submissions.</p>
  
  <p>Now I don't understand the exact relation between Bundles and Services.</p>
  
  <p>As I understand it to write a service is the right way to do so. At the same time I want to make my code reusable, so I can use it in further projects.
  My extension needs to have some JS and TWIGs I guess.</p>
  
  <p>So, is the right way for deploying my service to encapsulate in a bundle? Or are they bundles theirself? Or can they be deployed without encapsulating?</p>