title: What is content-type and datatype in an AJAX request?
body: <p>What is content-type and datatype in a POST request? Suppose I have this:</p>
  
  <pre><code>$.ajax({
      type : "POST",
      url : /v1/user,
      datatype : "application/json",
      contentType: "text/plain",
      success : function() {
  
      },
      error : function(error) {
  
      },
  </code></pre>
  
  <p>Is <code>contentType</code> what we send? So what we send in the example above is JSON and what we receive is plain text? I don't really understand.</p>