title: When would I use the "Mark directory as ..." option in IntelliJ IDEA?
body: <p>I am a newcomer finding my way around the IntelliJ IDE, for which I am currently using for coding in Scala.</p>
  
  <p>Right clicking in the Project window brings up a pop-up, with "Mark Directory As ..." as an option, with the following choices:</p>
  
  <ul>
  <li>Sources Root</li>
  <li>Test Sources Root</li>
  <li>Resources Root</li>
  <li>Test Resources Root</li>
  <li>Excluded</li>
  <li>Generated Sources Root</li>
  </ul>
  
  <p>Can I know would I use the "Mark Directory As ..." option? And also what would each of the choices do? I have tried looking around, but so far most websites have been rather vague with their explanations.</p>
  
  <p>Thanks for your help.</p>