title: lazy loading: progressive vs on-demand
body: <p>This is a conceptual question. In my particular case, I am using <a href="http://kenwheeler.github.io/slick/">slick.js</a> to create an image carousel for a website. Since these are high resolution photographs, I want to speed up the page load time by allowing the photographs to be loaded asynchronously instead of on page load.</p>
  
  <p>When looking through the documentation for this library, I saw the settings available for the 'lazyLoad' property with little information as to what those settings mean in practice.</p>
  
  <p>Essentially my question is, what is the difference between progressive and on-demand in the context of lazy loading.</p>