What is ionic and how is it related with HTML5?

Ionic is an HTML5 Mobile App Development Framework targeted at building hybrid mobile apps. Think of Ionic as the front-end UI framework that handles all the look and feel and UI interactions your app needs to be compelling. Kind of like "Bootstrap for Native", but with the support for a broad range of common native mobile components, slick animations and a beautiful design. 

Ionic framework needs native wrapper to be able to run on mobile devicesIonic is built and tested for mobile only. Internet Explorer does not support all the features of Ionic. Use separate applications for desktop and mobile.