title: In React, what is the function of the key attribute in html tag
body: <p>What is the function of the key attribute in the p tag? I inspected the dom, and I expected to see p tags for each element of the taco list as expressed in <code>&lt;p taco-1&gt;</code>, but it's just <code>&lt;p&gt;</code>. Any explanation will be much appreciated.             </p>
  
  <pre><code>{this.props.tacos.map( ( taco, i ) =&gt; {
      return &lt;p key={ `taco-${ i }` }&gt;{ taco }&lt;/p&gt;;
  })}
  </code></pre>