title: Differences between a multi-module project and a parent project
body: <p>In multi-module project in Maven, we have a parent pom with modules defined in <code>&lt;modules&gt;</code> tag, and in each module, we define which the parent pom is.</p>
  <ul>
  <li><p>Why this two-way definition?</p>
  </li>
  <li><p>Why not define the relationship between them just in the parent part of the modules</p>
  </li>
  <li><p>How am I supposed to reuse modules if they are always bound to one parent?</p>
  </li>
  </ul>