• Page transitions: Add special effects when users go from one page of your site to another. The new page loads while the effect is taking place, making it seem like the page loads immediately. 
• Preloader: A preloader adds a visual timer, such as a spinning circle, that shows visitors a page is loading. This is an indication that visitors should wait for the page to load. Preloaders can operate when visitors arrive at your site and when they navigate between your site’s pages.

If you use both a preloader and page transitions, the preloader will be active when visitors first arrive at your site, and page transitions will work when they navigate between your site’s pages.