A Single Page Application is an app that works dynamically within a browser. Instead of requiring pages to be reloaded as new information is requested, a single-page application dynamically rewrites the current page. If this sounds confusing, it's not. Gmail, Facebook, and Google Maps are all examples of single-page applications.
Because the page stays the same and isn't constantly refreshing, this leads to enhanced User Experience (UX). It, however, represents a challenge for Digital Adoption Platforms as they often rely on URL to change with every new screen.