title: joi.label , what does this method of joi schema validation do
body: <p>I just came across this line of code that I had to work on:</p>
  <p><code>Joi.array().label('Emails').items(Joi.string()).required()</code></p>
  <p>I particularly didn't understand what <code>.label('Emails')</code> was doing, so, I hit the documentation:</p>
  <blockquote>
  <p>Overrides the key name in error messages.</p>
  <pre><code>name - the name of the key.
  </code></pre>
  <p>const schema = {
  first_name: Joi.string().label('First Name') };</p>
  </blockquote>
  <p>and this particularly didn't make any sense to me. Because, is <code>First Name</code>, <code>Emails</code> particular parameters that can be passed? What is it overriding? What other arguments can we pass, etc. What is this method doing particularly?</p>