title: What's inside my rails ./bin directory?
body: <p>Ruby on Rails 4 introduced* the <code>./bin</code> directory. Inside of <code>./bin</code> are a few executables: <code>bundle</code>, <code>rails</code>, <code>rake</code>, <code>setup</code>, <code>spring</code>.</p>
  
  <p>My questions are:</p>
  
  <ol>
  <li>What do these executables do? Why do they exist?</li>
  <li>When are they invoked?</li>
  <li>Can I edit them? Why would I edit them?</li>
  </ol>
  
  <p>I've read the source of these files, and I've tried to Google their purpose, but I can't wrap my head around it. I'm looking for an in-depth explanation.</p>
  
  <p><sub>*I believe many of these files existed before Rails 4, just in different location.</sub></p>