title: What is `params.require(:person).permit(:name, :age)` doing in Rails 4?
body: <p>All the examples of strong parameters in Rails 4 docs use </p>
  
  <pre><code>params.require(:person).permit(:name, :age)
  </code></pre>
  
  <p>Could someone please deconstruct and explain what is occurring with <code>require</code> and <code>permit</code> here?</p>