An HTML5 app is a web-based app (also known as a mobile website) that users can access via their phone's browser. HTML5 apps are optimized for mobile devices, so they perform far better than full front-end sites. They're a great option for mobilizing existing websites and don't require any downloading.
We provide HTML5 apps in an effort to reach non-iOS/Android users (Blackberry, Windows, etc.) who aren't able to install our native apps. Our HTML5 apps are accessible on any modern smartphone with internet access. However, there are a couple limitations:
Native features like call, camera, voice recording, etc. that use your phone's built-in capabilities will not be usable through an HTML5 app.
Some tabs are incompatible with HTML5. Though you'll see them in your iOS/Android apps, they won't appear in the HTML5 version of your app.