title: What is CA certificate, and why do we need it?
body: <p>I've just read <a href="https://www.instantssl.com/ssl-certificate-products/https.html" rel="noreferrer">this article</a> about what is HTTPS service, and understand the basic of https. </p>
  
  <p>When requesting https content, the server will send a public key to browser, so that every time, the browser receive data will decrypted with the public key. </p>
  
  <p>My question is what is CA certificate for? Why do we need it? </p>