title: navigate different page without reload
body: <p>I am a noob to web development and  I have a question on link of a website. I found on some website on clicking links in navigation the page does not reload and the content changes. </p>
  
  <p>A good example would be this website itself. When you open this website i.e. <a href="http://stackoverflow.com">stackoverflow.com</a> and click on any other link on navigation link the url just changes to <a href="https://stackoverflow.com/questions">stackoverflow.com/questions</a> if clicked on Questions link. where as in my webpage it shows <code>index.html</code> at first and on clicking on About Us link in navigation it shows another URL as <code>aboutus.html</code>. </p>
  
  <p>Is this related to dynamic webpage? Could someone please help? Also the stackoverflow.com shows no extension like <code>.html</code>. Please help me to understand this. Thank you and would be obliged with your answer.</p>