title: What is the difference between a shim and a polyfill?
body: <p>Both seem to be used in web development circles, see e.g. <a href="https://github.com/Modernizr/Modernizr/wiki/HTML5-Cross-browser-Polyfills" rel="noreferrer">HTML5 Cross Browser Polyfills</a>, which says:</p>
  
  <blockquote>
    <p>So here we're collecting all the shims, fallbacks, and polyfills...</p>
  </blockquote>
  
  <p>Or, there's the <a href="https://github.com/kriskowal/es5-shim/" rel="noreferrer">es5-shim</a> project.</p>
  
  <p>In my current project we're using a number of these, and I want to stick them all in the same directory. So, what should I call this directory---<code>shims</code>, or <code>polyfills</code>?</p>