title: What are app.iml and proguard-rules.pro doing in my Android app directory?
body: <p>I am studying the file/directory structure of an Android Studio project.</p>
  
  <p>I don't understand the purpose of two files in /app directory:</p>
  
  <ol>
  <li>app.iml</li>
  <li>proguard-rules.pro</li>
  </ol>
  
  <p>May I have some explanation on these files? If I want to share my project with other programmers, then do I have to include these files or just whatever that goes under /src plus build.gradle is enough?</p>