title: why should we use subscribe() over map() in Angular?
body: <p>I am trying to take advantage of observables in angular2 and got confused on why should i use <code>map()</code> over <code>subscribe()</code>.
  Suppose i am getting values from a webApi, like this</p>
  
  <pre><code>  this.http.get('http://172.17.40.41:8089/api/Master/GetAllCountry')
  </code></pre>
  
  <p>Now using <code>subscribe(success, error, complete)</code> I can get all the values on the success callback and I can return the values on the complete callback. If I can do all theses functionalities then what is the need of <code>map()</code>? Does it give any advantage?</p>
  
  <p><strong>In short, why one should write like this</strong>:</p>
  
  <pre><code>this.http.get('http://172.17.40.41:8089/api/Master/GetAllCountry')
      .map(r=&gt;{})
      .subscribe(value =&gt; {
      }, error =&gt; error, () =&gt; {
  });
  </code></pre>
  
  <p><strong>when they can simply write this without the map function:</strong></p>
  
  <pre><code>this.http.get('http://172.17.40.41:8089/api/Master/GetAllCountry')
      .subscribe(value =&gt; {        
      }, error =&gt; error, () =&gt; {           
  });
  </code></pre>