title: Display subcategories on each category page wordpress
body: <p>I created this categories structure in my wordpress:</p>
  
  <pre><code>* Category1
      * SubCategory1(of Category1)
      * SubCategory2(of Category1)
  * Category2
      * SubCategory1(of Category2)
  * Category3
  </code></pre>
  
  <p>I need to list on each category its subcategories.(without any post)
  So when I will access the Category one -> I should see only the subcategories. If the Main category does not have any subcategory -> I should see its posts.</p>
  
  <p>My question1: <strong>What is the category page file name on wordpress? (I searched a lot but without any clear answer).</strong></p>
  
  <p>My question1: <strong>How to display for each main category(eg: Category1) only its children.</strong></p>