title: Using Consumer interface of Reactivex
body: <p>I'm new to ReactiveX. I was learning it from reading source-code. Everything was so clear but suddenly I got this word named "Consumer" which was an Interface. It was used in place of Observer.</p>
  
  <p>Can someone let me know what it exactly does?</p>
  
  <p>I followed several links but they just all said just one statement <strong>Consumer is a functional interface (callback) that accepts a single value.</strong></p>
  
  <p>I want to know the exact working of it.</p>
  
  <ol>
  <li>What is it?</li>
  <li>Why do we need it?</li>
  <li>How do you use it?</li>
  <li>Does it take the place of Observer? If YES, how and why?</li>
  </ol>